Numerical Study of Heat Transfer Around the Small Scale Airfoil Using Various Turbulence Models
24 Dec 2009-Numerical Heat Transfer Part A-applications (Taylor & Francis Group)-Vol. 56, Iss: 12, pp 946-969
TL;DR: In this article, a numerical investigation of low-Reynolds number flows with thermal effect around the MAV airfoils using various turbulence models, including an algebraic Baldwin-Lomax model, Spalart-Allmaras one equation, and two equation (k-ω and SST-kω) turbulence models were presented.
Abstract: A numerical investigation of low-Reynolds number flows with thermal effect around the MAV airfoils using various turbulence models, including an algebraic Baldwin-Lomax model, Spalart-Allmaras one equation, and two equation (k-ω and SST-k-ω) turbulence models, is presented. First, the thermal effect on the aerodynamic efficiency is studied for flow around a rectangular MAV wing, based on the NACA0012 airfoil section at low-aspect ratio (AR = 2) and an angle of attack equal to 0°. Second, details of the thermal effect are limited to the two-dimensional NACA0012 airfoil with chord length of 3.81 cm. This study shows that the improvement of aerodynamic efficiency (increase lift and reduce drag) is achieved by the generation of a temperature difference between extrados and intrados of the airfoil (by cooling the upper surface and heating the lower surface). The numerical results obtained with various turbulence models are in good agreement with experiment data, except the k-ω turbulence model. These results a...
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TL;DR: In this paper, the aerodynamic problems that must be addressed in order to design a successful small aerial vehicle are described, including the effects of Reynolds number and aspect ratio (AR) on the design and performance of fixed-wing vehicles.
Abstract: In this review we describe the aerodynamic problems that must be addressed in order to design
a successful small aerial vehicle. The effects of Reynolds number and aspect ratio (AR) on the design and
performance of fixed-wing vehicles are described. The boundary-layer behavior on airfoils is especially important
in the design of vehicles in this flight regime. The results of a number of experimental boundary-layer studies,
including the influence of laminar separation bubbles, are discussed. Several examples of small unmanned
aerial vehicles (UAVs) in this regime are described. Also, a brief survey of analytical models for oscillating and
flapping-wing propulsion is presented. These range from the earliest examples where quasi-steady, attached flow
is assumed, to those that account for the unsteady shed vortex wake as well as flow separation and aeroelastic
behavior of a flapping wing. Experiments that complemented the analysis and led to the design of a successful
ornithopter are also described.
102 citations
TL;DR: A comprehensive survey of the literature in the area of numerical heat transfer (NHT) published between 2000 and 2009 has been conducted by as mentioned in this paper, where the authors conducted a comprehensive survey.
Abstract: A comprehensive survey of the literature in the area of numerical heat transfer (NHT) published between 2000 and 2009 has been conducted Due to the immenseness of the literature volume, the survey
58 citations
TL;DR: In this paper, wind-tunnel experiments performed to investigate the aerodynamic and mechanical characteristics of micro air vehicles with flexible wings in different conditions of propeller type, motor power, and elevator deflections.
Abstract: The field of micro air vehicles is relatively immature; consequently, high-fidelity simulations do not yet exist for a generic aircraft. The fidelity of flight dynamic simulations is closely correlated to the reliability of models representing the vehicle's aerodynamic and propulsion characteristics in the entire flight envelope, including the nonlinear region. This paper discusses wind-tunnel experiments performed to investigate the aerodynamic and mechanical characteristics of micro air vehicles with flexible wings in different conditions of propeller type, motor power, and elevator deflections. Visual image correlation was used to measure the deformation of the flexible wings to quantify general features such as variations in aerodynamic and geometric twist angle. Aerodynamic and propulsion results were used to formulate empirical models of the relevant coefficients in the form of multiple linear regressions and to estimate the effectors' functional dependencies and interactions. High-order nonlinear interactions were confirmed between the coefficients of lift, drag, and pitching moment with the independent variables. The rates of the dependencies with elevator deflections and angle of attack were found, to some extent, to be motor voltage and dynamic pressure dependent, evincing a strong coupling with the propeller speed.
24 citations
TL;DR: In this paper, a dynamic model and drag coefficient calculations of a temperature probe descent into ocean water are presented to predict the depth of the probe during descent into the ocean during a measurement of ocean temperatures.
Abstract: Computational fluid dynamics techniques have been applied to model fluid flow in the vicinity of oceanographic temperature probes A major goal of the modeling effort is the determination of drag coefficients for probe descent into ocean water These drag coefficients can be used, in conjunction with a dynamic model of the probe, to predict the depth of the probe during descent Accurate depth information is essential for the proper measurement of ocean temperatures and, consequently, ocean heating associated with climate change Until recently, probe depths were predicted with the use of experimental calibrations which relate time-of-flight and depth Those calibrations are limited in their accuracy, they are confined to conditions that match the experiments from which the calibrations were determined, and they are unable to account for variations in quantities such as the drop height or initial probe mass The dynamic model and drag coefficient calculations presented here are, to the best knowledge of t
20 citations
Additional excerpts
...It is expected that the quality of the results would be maintained even if less sophisticated turbulence models were used [ 35 ]....
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TL;DR: In this article, the effect of heat transfer upon the aerodynamic performance of a pitching and plunging NACA0012 airfoil in the low Reynolds number flow regime with particular emphasis upon the airfoils's lift and drag coefficients was investigated.
Abstract: The unsteady low Reynolds number aerodynamics phenomena around flapping wings are addressed in several investigations. Elsewhere, airfoils at higher Mach numbers and Reynolds numbers have been treated quite comprehensively in the literature. It is duly noted that the influence of heat transfer phenomena on the aerodynamic performance of flapping wings configurations is not well studied. The objective of the present study is to investigate the effect of heat transfer upon the aerodynamic performance of a pitching and plunging NACA0012 airfoil in the low Reynolds number flow regime with particular emphasis upon the airfoil's lift and drag coefficients. The compressible Navier–Stokes equations are solved using a finite volume method. To consider the variation of fluid properties with temperature, the values of dynamic viscosity and thermal diffusivity are evaluated with Sutherland's formula and the Eucken model, respectively. Instantaneous and mean lift and drag coefficients are calculated for several temperature differences between the airfoil surface and freestream within the range 0–100 K. Simulations are performed for a prescribed airfoil motion schedule and flow parameters. It is learnt that the aerodynamic performance in terms of the lift C L and drag C D behavior is strongly dependent upon the heat transfer rate from the airfoil to the flow field. In the plunging case, the mean value of C D tends to increase, whereas the amplitude of C L tends to decrease with increasing temperature difference. In the pitching case, on the other hand, the mean value and the amplitude of both C D and C L decrease. A spectral analysis of C D and C L in the pitching case shows that the amplitudes of both C D and C L decrease with increasing surface temperature, whereas the harmonic frequencies are not affected.
10 citations
References
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"Numerical Study of Heat Transfer Ar..." refers methods in this paper
...For the RANS equations, two different spatial discretization schemes are available: Roe’s flux difference splitting scheme [42] and Van Leer’s flux vector splitting scheme [43]....
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1,648 citations
"Numerical Study of Heat Transfer Ar..." refers methods in this paper
...For the RANS equations, two different spatial discretization schemes are available: Roe’s flux difference splitting scheme [42] and Van Leer’s flux vector splitting scheme [43]....
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