Theses supervised by Prof. Dr. Beşir Şahin
32 theses · Çukurova University
Wind energy potential in some locations of Turkey
ABSTRACT M.Sc. THESIS THE WIND ENERGY POTENTIAL IN SOME LOCATIONS OF TURKEY MEHMET BİLGİLİ DEPARTMENT OF MECHANICAL ENGINEERING INSTITUTE OF NATURAL APPLIED SCIENCES ÇUKUROVA UNIVERSITY Supervisor : Prof. Dr. Beşir ŞAHİN Year: 2003, Pages: 80 Jury : Prof. Dr. Beşir ŞAHİN Prof. Dr. RTuğrul O?ULATA Assoc. Prof. Dr. Orhan BÜYÜKAL AC A The aim of this study is to establish the meteorological basis for the assessment of wind energy resources in East Mediterranean Region of Turkey and provide suitable data for evaluating the potential wind power. For this purpose, hourly wind data which were observed between the years 1992 and 2001 at Antakya, İskenderun and Dörtyol Meteorological Stations were used. Calculations were made using appropriate computer programs which were prepared for study and a numerical model which is known as WASP (Wind Atlas Analysis and Application Program). The dominant prevailing wind directions, the mean values, the daily, monthly and annual variations and the frequency distributions were determined. Results were classified according to the height above ground level. Finally, the Wind Atlas of these regions, in the form of contours of constant wind speed and wind potential, were produced. Key Words: Wind energy, Frequency distribution, Wind Atlas, WASP
Investigation of flow characteristics in heat exchangers of various geometries
INVESTIGATION OF FLOW CHARACTERISTICS IN HEATEXCHANGERS OF VARIOUS GEOMETRIESNurhan Adil ÖZTÜRKABSTRACTThe aim of the present study is firstly to investigate details of flow structure inthe upstream and downstream of a circular cylinder base mounted on a flat surface indeep water flow for the Reynolds number ranging from 750 to 9600. The analysis ofthe instantaneous and time-averaged flow data demonstrates that the horseshoevortices take place in the base of the cylinder in three dimensional form. Thesevortices magnify the scour and entrainment processes.Secondly, experimental investigation of flow structure in the passage of arectangular duct with a built-in single circular cylinder was conducted. A duct with anarrow gap was designed to simulate fin-tube heat exchanger containing a singlecircular cylinder. Development of the entrainment process between main flow andwake flow regions is magnified by immigrating helical horseshoe vortex systememerging from upstream of the cylinder. The occurrence and development ofboundary layer separation and formation of horseshoe vortices upstream of thecylinder in close region of both upper and lower plate surfaces and merging of thesedeveloping horseshoe vortices which form a primary vortex system are alsoobserved.Finally, the flow characteristics of multiple circular cylinder arrangements inthe passage of rectangular duct were examined in order to reveal the mechanisms ofhydrodynamics which are mostly responsible for the enhancement of the heattransfer rate. In the case of staggered cylinder arrangements, the flow is restless, i.e.,accelerations and decelerations of flow continuously happens to cause a high rate offluctuations. The entrainment process of flow the particularly in the junction regionsis significant.Keywords: PIV, horseshoe vortex, cylinder, turbulent flow, water flow
Investigation of horseshoe vortex system
ABSTRACTM.Sc. THESISINVESTIGATION OF HORSESHOE VORTEX SYSTEMElif ÖZKULDEPARTMENT OF MECHANICAL ENGINEERINGINSTITUTE OF NATURAL AND APPLIED SCIENCESUNIVERSITY OF ÇUKUROVAAdvisor : Prof. Dr. Beşir ŞAHİNYear: 2006, Pages: 56Jury : Prof. Dr. Beşir ŞAHİNAssoc. Prof. Dr. Hüseyin AKILLIAssoc. Prof. Dr. Galip SEÇKİNThe primary aim of this study is to examine the nature of the horseshoe vortexsystem and its interaction in the base of vertical plate mounted on a flat surface indeep water flow. Flows including horseshoe vortex system have been attractingconsiderable attention due to its importance in engineering applications.Flow fields in side and plan-view planes were visualized using dye and particleimage velocimetry technique to study the structure and development of horseshoevortex system qualitatively and quantitatively.The range of Reynolds numbers base on the plate width are 17100 ⤠Rep â¤31200. The analysis of the cinema of instantaneous flow data and time-averagedvelocity vectors field, patterns of streamlines and corresponding vorticity patternsincluding dye visualizations clearly identified the development and interactions ofthe horseshoe vortex system.Keywords: PIV, horseshoe vortex, vertical plate, turbulent flow, water flow
Aerodynamics of a model bus
The ultimate goal of this work is to examine the turbulent, 3D flow around a bus-shaped body by means of CFD. Another goal of this study is to show the accordance between the numerical and experimental results. In the present study, RANS k-? turbulence model is employed to simulate the flow around the vehicle, and the results of the experiments performed by PIV are used to validate the corrections of the numerical simulation. A comparison of predicted results for time-averaged flow data, particularly, around the forward face of the model with the experimental results of Particle Image Velocimetry (PIV) showed that numerically predicted present results and experimental results agreed well. The flow is assumed to be incompressible, viscous, turbulent, and steady flow. Key Words: Aerodynamics, Bus, Reynolds Average Navier Stokes (RANS), k-? Turbulence Model
Study of the flow around a bus model
Land transportation is the most widely used passenger and freight transportation in Turkey. It is known that a 10% drag reduction leads to approximately a 5% reduction of the fuel consumption of a bus at a common highway speed. An estimated total savings of $100 million per year can be recognized in Turkey alone for just a 5% reduction in fuel use in intercity passenger transportation by buses. Detailed knowledge of the aerodynamic characteristics of passenger vehicles could lead to find out new solutions to reduce fuel consumption and emissions and improving the vehicle performance and passenger comfort.In this study, flow structures around a rectangular body and two different bus models are analyzed using both particle image velocimetry (PIV) and flow visualization techniques. Measurements were performed at several planes which were selected to highlight the aerodynamic characteristics of the models. The instantaneous and time-averaged velocity vector maps, vorticity contours, streamline topology and turbulence characteristics of flow fields are presented.
Süpürme açisi küçük delta kanat üzerinde girdap oluşumu
In this work, vortical flow structure of a delta wing of low sweep angle was investigated both qualitatively and quantatively using dye visualization and a laser based Particle Image Velicimetry (PIV) technique. Firstly, the flow structure in close region of the stationary delta wing and formation of the vortex breakdown were studied by varying the angle of attack within the range of 7o? ? ?17o. Secondly, changes in flow structure were observed varying the yaw angle of the delta wing within the range of 0o? ? ?15o. In summary, patterns of time-averaged vorticity, < ? >, streamline, < ? >, distribution of velocity vectors,, and transverse velocity component, /U, for various angles of attack and yaw angles were obtained in order to reveal the flow mechanism in plan-view plane adjacent to the surface of the wing and over the crossflow planes.
Flow characteristics of diamond and lambda wings at different flight conditions
The aim of this study is to investigate the time-averaged flow structure around a nonslender diamond and lambda wing using a laser based 3-dimessional Particle Image Velocimetry (PIV) technique. The flow structure in close region of the stationary diamond wing surface and formation of the vortex breakdown were studied by varying the yaw angle of the wing within the range of 0 ? ? ? ?15 ? for the angle of attack of ????? and ??? .Secondly, the flow structure in the near-surface and other crosssections of the wing and formation of the vortex breakdown were investigated by varying the angle of attack of the wing within the range of 7o? ? ?17o.Finally, a lambda wing is subjected to small-amplitude perturbations over a range of periods to simulate leading-edge vortex control concepts. Perturbations near the inherent frequency of the predominantly unsteady flow event on the stationary wing yield substantial changes of the near surface flow structure. Experimental analyses are composed of time-average patterns of streamlines, contours of vorticity distributions, Reynolds stress correlations, transverse and streamwise velocity components, distribution of fluctuating velocities and turbulent kinetic energy.
Investigation of flow characteristics around a single and staggered slotted-cylinders
The aim of this experimental study is to determine the flow characteristics of a single and multiple slotted-staggered cylinders placed in a rectangular water channel with a narrow gap using the Particle Image Velocimetry technique. Qualitative flow visualization was initially employed in order to observe the overall nature of the vortical flow patterns for different configurations of cylinders. Quantitative flow visualization was secondly employed for whole configurations of cylinders in order to understand the physics of complex flow behaviour that gives rise to unsteady loading with the eventual intent of implementing control schemes to enchance the rate of heat transfer hydrodynamically.
Design and optimization of microwave oven
The hereby thesis was prepared in order to conduct the thermal calculations of the bakery ovens with rotating carts especially by examining the thermo-chamber. In the first section it was referred to detailed information regarding bread which was the material to be cooked, and the constitution process of bread was explained. In the following two sections the presentation of oven was introduced. Main groups of oven, security systems and vapor delivery systems were presented. And in the fourth and the last section all calculations were made. Firstly thermal calculations and then cost calculations were prepared. All these calculations were performed for each thermo-chamber anticipated to operate with three different fuel types and total fuel cost for same bread type was found.
Experimental and numerical studies of flow characteristics around a ground vehicle
Flow around ground vehicles is fully three-dimensional and turbulent. Large-scale separation and circulation regions, a complex wake flow, long trailing vortices and the interaction of boundary layer flows can be given as typical characteristics of the flow around ground vehicles. A Thorough understanding of the structure of the flow around ground vehicles is essential for the designer when developing a new road vehicle because the shape of vehicles has a strong influence on the aerodynamic drag, fuel consumption, noise production and road handling. The simplified vehicle shape employed by Ahmed et al. (1984) retains some main features of the flow around real cars including fully three-dimensional large regions of separation elongated downstream of the vehicle, large coherent vortex structures and unsteadiness.Thus, the aim of the present study is to investigate characteristics of flow structures around ground vehicles with the help of Ahmed body using both experimental and numerical methods. Therefore, 1/4 scale Ahmed body having 25o slant angle was employed. The Reynolds number based on the body heights, H and the free stream velocity, U was ReH=1.48x104. Investigations were conducted in two parts. In the first part of the study, particle image velocimetry (PIV) technique was used for the measurement of the instantaneous velocity fields around the Ahmed body. In addition, measurements were performed at several planes which were selected to highlight the aerodynamic characteristics of the body. In the second part of the study, Large Eddy Simulation (LES) method was used to resolve the flow structures around the Ahmed body, numerically. Most of the flow features around the Ahmed body such as the formation of trailing vortices, separation and re-circulatory flows were well predicted. Finally the instantaneous and time-averaged velocity vectors maps, vorticity contours, streamline topology and turbulence characteristics of the flow fields were presented and discussed in details.
Experimental and numerical investigation of flow around spheres
The aim of the present study was to investigate the flow characteristics around single and dual spheres in three different locations with respect to flow condition. Initially the single sphere was positioned in the free-stream flow to observe the flow characteristics for the purpose of comparisons. Effects of the free-surface flow on the flow structures downstream of the single sphere were investigated for four different submerging elevations. Interaction between laminar boundary layer and wake flow downstream of the single sphere was also studied using four different embedding elevations of the sphere from the plain plate. On the other hand, flow structures around two spheres with tandem arrangement were studies. Here, four different separation distances were conducted between spheres. Secondly, experiments and computations were performed on the side-by-side spheres with different separation distances between spheres. Finally, flow characteristics around the segregated spheres were investigated using three different separation distances and three different separation angles. All investigated cases associated with the single sphere and dual spheres were performed at the Reynolds number of 5,000 with respect to the free-stream velocity and sphere diameter. In addition, for calculation of the turbulence characteristics, Large Eddy Simulation using a dynamic Smagorinsky sub-grid scale was used and experiments were performed using the Particle Image Velocimetry technique. The interaction between the free surface and wake flow increases by decreasing the submerging elevation. Finally, the obtained results revealed that interaction between the spheres varies as a function of arrangement of spheres.
MICRO-PIV measurements of induced-charge electro-osmotic flows
In this work, induced-charge electro-osmosis (ICEO) around single and multiple gold-coated stainless steel rod(s) was investigated. The rod(s) positioned at the center of a straight microchannel connecting two fluid reservoirs on either end. The microchannel was filled with pure and polymer-containing 1 mM KCl solution, which was seeded with 0.5 ?m diameter carboxylate-modified spherical particles. The ICEO flow around the metallic rod(s) was measured using the micro particle image velocimetry (micro-PIV) technique as functions of the AC electric field strength and frequency. The present study provides experimental data about the ICEO flow in the weakly nonlinear limit of thin double layers, in which the charging dynamics of the double layer cannot be presented analytically. Flow observed around the rod(s) was quadrupolar, which drived liquid towards the rod(s) along the electric field and forced it away from the rod(s) in the direction perpendicular to the imposed electric field. The measured ICEO flow velocity was proportional to the square of the electric field strength, depended on the applied AC frequency and polymer concentration.
Flow control of a cylinder in shallow water using perforated cylinder
The aim of this experimental study was to control the vortical flow structure downstream of a circular cylinder (inner cylinder) as well as the surrounding outer perforated cylinder in shallow water flow. Experiments were performed using both special dye visualization and a laser-based particle image velocimetry technique. Experiments consisted of two parts; i) Vortex shedding behavior around a perforated cylinder was investigated with the porosity, ß in the range of 0.1?ß?0.8 for the Reynolds number of ReDo=10,000 and outer perforated cylinder diameter of Do=100mm and ii) The effects of porosity, ß and the inner cylinder diameter to the outer perforated cylinder diameter ratio, Di/Do on the unsteady flow characteristics around both inner and outer perforated cylinders were analyzed. Experiments were conducted for nine different diameter ratios within the range of 0.25?Di/Do?0.8, 15 different porosity, ß and three different Froude numbers, (Fr=0.2, 0.3 and 0.4). PIV measurements showed that the porosity, ß and diameter ratio, Di/Do have a substantial effect on the suppression of vortex shedding and the consequent Karman Vortex Street. The velocity fluctuations in the wake region of inner cylinders were substantially affected by the existence of outer perforated cylinder which is concentrically located around the inner cylinder. The values of the optimum porosity, ß to control the unsteady flow structure were found to be ß=0.75, 0.6, 0.55 and 0.4 for the diameter ratios of Di/Do=0.25, 0.5, 075, and 0.9, respectively.
Energy and exergy analysis of a steam power plant
In this study, the energy and exergy analyses of the steam power plant have been performed with three different operating loads (100%, 70% and 40%). This steam power plant is designed to operate at a subcritical steam conditions and has a power capacity of 660 MW at full load. The primary objectives of this study are to analyze the system components separately and to identify and quantify the sites having largest energy and exergy losses. Influences of three different loads on the useful power, reversible power and irreversibility have been investigated for each component. In addition, the second law efficiency of system components and the overall efficiency of the plant have been computed. Energy losses mainly occur in the condenser and that exergy losses mainly take place in the boiler. According to these results, the exergy analysis is more significant compared to the energy analysis. It is found that if the exergy losses are reduced, the power plant efficiencies are positively affected. Key Words: Energy Analysis, Exergy Analysis, Operating Load, Second Law Efficiency
Investigation of flow characteristics and heat transfer enhancement of various duct geometries
The aim of this study is to determine the flow characteristics and thermal efficiency in various ducts geometries numerically and experimentally. The whole study has been conducted for Reynolds numbers in the range of 3000≤Re≤6000. Firstly, the effect of aspect ratio, s/H on heat transfer enhancement and on flow structures was aimed to be examined. Therefore, the corrugated duct geometries were designed for three different aspect ratios such as s/H=0.1, 0.2, 0.3 and various phase shift angles, φ of corrugated channels. Thermal efficiency of these geometries were examined numerically in order to optimize the aspect ratio, s/H. Afterwards, experimental studies were conducted in order to identify hydrodynamic structures and verify findings of numerical solution using Particle Image velocimetry (PIV). Throughout the study, three different phase angles, φ=0̊, 90̊ and 180̊, were utilized. Velocity distributions, patterns of streamline and corresponding turbulent statistics were determined experimentally and numerically in order to reveal hydrodynamics and thermal efficiency of the corrugated channel flow. In numerical calculations, standard k-ε turbulent model was utilized. As a result of numerical studies, Nusselt number, Nu friction factor, f and efficiency index, η were calculated for different corrugated channel geometries. Consequently, it was observed that numerical and experimental results were extremely compatible with each other
Efficiency analysis of an installed wind farm
In this study, energy analysis and efficiency study of turbines of a wind farm were performed using data of wind speed, wind direction, air temperature and electric generation, of five selected turbines. Wind energy losses of the plant, monthly and daily performance of turbines were carried out. Parameters influencing the results were also examined in detail. Aerodynamic analysis of turbines was conducted using data of five turbines. Analysis of factors affecting system performance, Betz criteria, power coefficient, energy balance and exergy balance were conducted. Magnitude of wind speeds where turbines start and stop energy generation and influences of these wind speeds on power production and energy losses of five turbines were examined. Consequently, clarifications on the reasons of the losses during conversion of wind power into electric energy, and clarifications on the reasons of instantaneous fluctuations in efficiencies were aimed to be explained. Interactions between aerodynamic parameters during power generation were also reported.
Energy analysis of solar-powered absorption cooling system in Mersin
In this study, solar-powered absorption cooling system located in the province of Mersin was analyzed using hourly atmospheric temperature and solar radiation data. Ammonia-water as refrigerant-absorbent pairs and evacuated tube collector were chosen for the design of solar-powered absorption cooling system. Required solar collector areas were calculated for heat loads of the refrigerated space. According to obtained results, Coefficient of Performance (COP) values were also changed for the 23rd day of chosen months. The maximum COP values were observed in May, while the lowest values were seen in July and August. The maximum solar radiation was observed on 23 June at 01:00 pm. At this time, COP was calculated as 0.786, while solar radiation was 0.878 kW/m2. The optimum collector area required for cooling is determined as 50 m2 for a refrigerated space of 30 m2.
Flow characteristics and heat transfer enhancement of sinusoidal corrugated channels
In this study, flow characteristics and heat transfer enhancement in various sinusoidal corrugated channels were investigated. The channel height and phase shift effects on the flow structures and thermal performances were examined for Reynolds numbers in the range of 2500≤Re≤7500. The geometrical configurations of this study cover three different channel heights (Hmin/Hmax=0.36, 0.54, 0.72) and phase shift angles (φ=0°, 90°, 180°). Firstly, flow characteristics in corrugated channels were investigated both experimentally and numerically. Experiments were conducted using the Particle Image Velocimetry (PIV) technique to compare with the results obtained from the numerical simulations. Afterwards, the hydrodynamic structures and thermal performance of the sinusoidal corrugated channels were studied. Velocity distribution, turbulence intensity, local and averaged Nusselt numbers, Nu and friction factor, f were calculated for various configurations. Finally, thermal performance factor (TPF) were also calculated to determine the optimum channel configuration and operating condition.
Effect of yaw angle on vortex formation over a slender delta wing
In this study, effects of yaw angle, β on the vortical flow over a delta wing which has a 70° sweep angle, Λ were investigated qualitatively and quantitatively by means of different experimental techniques. Experiments were performed as a function of angles of attack, in the range of 25°≤α≤35° and yaw angles in the range of 0°≤β≤20°. Leading edge vortex breakdown locations, trajectories of these vortices and their interactions were observed using dye visualizations. Time-averaged velocity vectors, pattern of streamlines, velocity components, contour of vorticity distributions, turbulence statistics such as Reynolds stress correlations, distribution of fluctuating velocities and turbulent kinetic energy were determined using instantaneous velocities measured by Stereo Particle Image Velocimetry (Stereo PIV). Separation and reattachment lines on the surface of the delta wing were also observed using surface oil visualization. Distribution of pressure coefficients Cp over the surface of the delta wing were calculated using pressure measurements. Results revealed that in the absence of the yaw angle, β symmetrical flow structure forms over the delta wing but when delta wing is yawed symmetrical flow structure is altered considerably. Windward side vortex breakdown location moves upstream, close to the apex of delta wing. Trajectories of the vortices moved towards the central axis of the delta wing. Disordered vortices are observed to spread over the surface of the delta wing. Leeward side vortex breakdown location moves downstream of the delta wing and its trajectory slips towards the leading edge. Furthermore, variation of yaw angles, β are observed to have significant effects on the distribution of velocity components, turbulence statistics and distribution of pressure coefficients, Cp over the surface of the delta wing.
Effects of yaw angle on vortex formation downstream of a slender delta wing
In the present work, basic features of counter rotating pair of leading edge vortices and vorticity concentrations downstream of vortex breakdowns in end-view planes of the delta wing with 70° sweep angle, Λ were experimentally studied both qualitatively and quantitatively using Rhodamine dye and the particle image velocimetry (PIV) technique. Experiments were conducted by altering angles of attack within the range of 25°≤α≤35° and yaw angles, β within the range of 0°≤β≤20°. Present investigation focused on crossflow structures in sequentially- located at five different end-view planes along the cord axis, C at locations x/C=0.2, 0.4, 0.6, 0.8 and 1.0. A trajectory of leading edge vortices, locations of vortex breakdown, and vorticity concentrations occurring downstream of vortex breakdowns and their interactions were observed using dye visualizations. Time-averaged velocity vectors , pattern of streamlines,<ψ> velocity components, u and v, contour of vorticity distributions, <ω> and root mean square of streamwise velocity, /U and transverse velocity, /U components were determined by the PIV technique. When the delta wing is yawed, macro scale symmetrical flow structures are altered considerably. The windward side vortex breakdown location moves towards the apex of delta wing. Trajectories of leading edge vortices slide sideway close to the central axis of the delta wing.
Aerodynamics of pitching delta wing with yaw angle
In this study, a slender delta wing with 70° sweep angle, Λ was oscillated about its mid-cord in a vertical plane according to the equation α(t)=αm+αosin(ωet). The values of mean angle of attack, αm were taken as 25°, 30° and 35°. The yaw angle, β was varied over the range of 0°≤ β ≤ 16°. The delta wing was sinusoidally pitched within the range of period of time, Te=2π/ωe, 5s≤ Te ≤60s and the reduced frequencies were set as K=0.16, 0.25, 0.49, 1.96 and lastly amplitude of pitching motions was varied within the range of ±5°≤ αo ≤ ±10°. The main aim of this study is to observe the effect of pitching motion of delta wing on the formation of vortex breakdown and structures of vortical flow downstream of vortex breakdown under yaw angle, β using a dye visualization and the particle image velocimetry (PIV) technique. Leading edge vortex breakdown position on the windward side moves towards the apex of the delta wing and vorticity concentrations spread over the most part of the delta wing. But the other leading edge vortex on the other side moves in free-stream flow direction without bursting at different yaw angles, β.
Assessment of an integrated system with coal fired power plant for multigeneration
In this thesis, a novel multigeneration energy system was introduced based on a conventional steam power plant. This system consists of four sub-systems, namely, waste heat recovery system using organic Rankine cycle, vapor compression refrigeration system, thermal vapor compression desalination system and greenhouse heating system. Energy and exergy analyzes were conducted for defining the efficiency of the sub-systems and the overall efficiency of the multigeneration energy plant. In order to better understand the system performance and to demonstrate the potential for improvement of the multigeneration system, exergoeconomic and environmental analyzes were also performed. The results revealed that the overall efficiency increased when a conventional steam power plant was converted into a multigeneration energy system. As a result, CO2 emissions were reduced because of the lower consumption of coal for the same amount of electricity generation. Fossil fuel consumption and global climate change increase the advantage and importance of an efficient multigeneration power plant.
Aerodynamics and statistical analyses of conventional and diffuser augmented wind turbines
In this study; the wind energy production status of the World, Europe, and Turkey were reviewed in comparison with the other renewable energy sources. More specifically, wind energy situation of the World and Turkey was also examined in detail. Firstly, wind power estimation and analysis of a considered region in Turkey were conducted by statistical techniques. Secondly, the evaluation of the power generation and the efficiency of a wind farm located in Turkey were performed. Assessments of the aerodynamics of running wind turbines and evaluations of their operational procedure in the active wind farms in Turkey were conducted in the third and fourth stages of the study. The following three distinct studies include modeling and estimation of parameters such as aerodynamic structure, power output, and the power coefficient, utilizing artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). On the other hand, the comparisons by means of power generations and aerodynamics of currently operating selected wind turbines were reported in the eighth part of the study. In the following two parts of the study, it was focused on examining the increase of wind power output originated from the wind speed enhancement as a result of the innovative casing system of wind turbines. The most effective casing types and their related designs found in the literature are also evaluated within this thesis. Finally, the increase of wind speed in some designed wind turbine casing structures and flow characteristics inside these casing structures were investigated in detail, utilizing numerical and experimental methods. Keywords: Aerodynamics of conventional bare wind turbines, analysis of wind power, design parameters of diffuser augmented wind turbines, wind energy
Ground effect on the aerodynamic parameters and flow characteristics of a non-slender delta wing
In this study, the ground effect on the flow structure and aerodynamic coefficients of the non-slender delta wing with a sweep angle of 40° was investigated experimentally. The flow visualization experiments were carried out at Reynolds numbers, Re=10^4 and 2x10^4 for various angles of attack, α and ground distances, h/c. The results demonstrated that the ground effect causes earlier vortex breakdown and more disordered and unsteady flow structure formed on the delta wing compared to the ground free case at the Reynolds number, Re= 10^4. But when Reynolds numbers, Re is increased from 10^4 to 2x10^4 value, the impact of the ground on the vortical flow structure and the vortex breakdown position is reduced and it has virtually no effect at angles of attack of α=8°, and 14°. For the wind tunnel experiments, the Reynolds number, Re was taken as, 1.296x10^5 at different angles of attack, α and ground distances, h/c. Results revealed that ground effect gives rise to higher lift coefficients, CL compared to the ground free case. The lift increment can be attributed to the RAM pressure effect and dynamic air cushion between ground and delta wing surface. The Particle Image Velocimetry (PIV) experiments were carried out to investigate the impact of the ground on the time-averaged streamline pattern, vorticity concentrations and velocity fluctuations at the Reynolds number, Re=15.73x10^3. Results displayed that the ground effect brings about outboard movement of primary vortices compared to ground free case. Also, the size of the primary vortices gets higher under the impact of the ground.