Effect of turbulence modeling for the prediction of flow and heat transfer in rotorcraft avionics bay

2019-12-01
In this paper, four turbulence models are compared on the basis of the predictions they produce for the flow and heat transfer in the avionics bay area of a rotorcraft. The turbulence models studied are the standard k-s, Renormalization Group (RNG) k-epsilon, realizable k-epsilon, and Shear-Stress Transport (SST) k-omega model. The avionics bay used in the study houses avionics equipment mounted on the floor and on a rack inside the bay to mimic a realistic distribution of equipment in actual rotorcraft. The avionics bay incorporates a cooling system consisting of a fan that intakes ambient air via a forced-convection method and an exhaust, with the purpose of keeping the avionics equipment temperatures below their operational limits. The turbulence levels, flow and thermal fields are investigated and compared in order to quantify the differences between the predictions of the turbulence models used in computations. It is observed that the use of the standard and realizable k-epsilon models mostly produce similar flow and thermal results across the bay area, while the largest differences between the predictions are found with the RNG k-epsilon and the SST k-omega turbulence models especially at the locations in the vicinity of the fan impingement. Comparing the avionics equipment surface temperature predictions, the standard and realizable k-epsilon turbulence models are observed to produce slightly more conservative results. The average variation between the surface temperature predictions by all models is less than 3.5 K, indicating that this parameter is considerably insensitive to the selected turbulence model. A close examination of the fan jet region starting from the fan inlet revealed generally similar predictions of flow and thermal features by all turbulence models. The maximum variation in the velocity and temperature predicted by all turbulence models is 2.2% and 0.1% of the fan inlet conditions, respectively. Large differences in turbulence intensity were observed depending on the location downstream of the fan jet and the turbulence model used. (C) 2019 Elsevier Masson SAS. All rights reserved.
AEROSPACE SCIENCE AND TECHNOLOGY

Suggestions

Effect of Thickness-to-Chord Ratio on Flow Structure of a Low Swept Delta Wing
Gulsacan, Burak; Sencan, Gizem; Yavuz, Mehmet Metin (American Institute of Aeronautics and Astronautics (AIAA), 2018-12-01)
The effect of thickness-to-chord (t/C) ratio on flow structure of a delta wing with sweep angle of 35 deg is characterized in a low-speed wind tunnel using laser-illuminated smoke visualization, particle image velocimetry, and surface pressure measurements. Four different t/C ratios varying from 4.75 to 19% are tested at angles of attack, 4, 6, 8, and 10 deg, for Reynolds numbers Re =1 x 10(4) and 3.5 x 10(4). The results indicate that the effect of thicknessto-chord ratio on flow structure is quite substan...
Estimation of pico-satellite attitude dynamics and external torques via Unscented Kalman Filter
Söken, Halil Ersin (FapUNIFESP (SciELO), 2014-01-01)
In this study, an Unscented Kalman Filter (UKF) algorithm is designed for estimating the attitude of a picosatellite and the in-orbit external disturbance torques. The estimation vector is formed by the satellite's attitude, angular rates, and the unknown constant components of the external disturbance torques acting on the satellite. The gravity gradient torque, residual magnetic moment, sun radiation pressure and aerodynamic drag are all included in the estimated external disturbance torque vector. The sa...
On the wake pattern of symmetric airfoils for different incidence angles at Re=1000
Kurtuluş, Dilek Funda (SAGE Publications, 2016-06-01)
In the current study, numerical simulations are performed in order to investigate effects of incidence angle and airfoil thickness on alternating vortex pattern of symmetric airfoils at Re = 1000. This alternating vortex pattern is found to be significantly varying in shape as the incidence angle increases. The results are obtained with 1 degrees increment from 0 degrees to 41 degrees and then with 10 degrees increment from 40 degrees until 180 degrees. The instantaneous and mean vortex patterns are investi...
Nonlinear flutter calculations using finite elements in a direct Eulerian-Lagrangian formulation
Seber, Guclu; Bendiksen, Oddvar O. (American Institute of Aeronautics and Astronautics (AIAA), 2008-06-01)
A fully nonlinear aeroelastic formulation of the direct Eulerian-Lagrangian computational scheme is presented in which both structural and aerodynamic nonlinearities are treated without approximations. The method is direct in the sense that the calculations are done at the finite element level, both in the fluid and structural domains, and the fluid-structure system is time-marched as a single dynamic system using a multistage Runge-Kutta scheme. The exact nonlinear boundary condition at the fluid-structure...
Investigation of rotor wake interactions in helicopters using 3d unsteady free vortex wake methodology
Yemenici, Öznur; Uzol, Oğuz; Department of Aerospace Engineering (2010)
This thesis focuses on developing and examining the capabilities of a new in-house aerodynamic analysis tool, AeroSIM+, and investigating rotor-rotor aerodynamic interactions for two helicopters, one behind the other in forward flight. AeroSIM+ is a 3-D unsteady vortex panel method potential flow solver based on a free vortex wake methodology. Validation of the results with the experimental data is performed using the Caradonna-Tung hovering rotor test case. AeroSIM+ code is improved for forward flight cond...
Citation Formats
A. Akin and H. S. Kahveci, “Effect of turbulence modeling for the prediction of flow and heat transfer in rotorcraft avionics bay,” AEROSPACE SCIENCE AND TECHNOLOGY, pp. 0–0, 2019, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/43041.