Low speed lateral-directional dynamic stability analysis of a hypersonic waverider using unsteady Reynolds averaged Navier Stokes forced oscillation simulations

Abstract Aerodynamics phenomena in compressors are highly unsteady and turbulent. Selecting a proper turbulence-modeling method is significant to reveal the complex flow mechanism in turbomachines. In the current paper, the shear stress transport (SST) model as an unsteady Reynolds-averaged Navier-Stokes (RANS) method, the scale-adaptive simulation (SAS) model, and the zonal wall-modeled large eddy simulation (zonal-LES) as two hybrid scale-resolving simulation approaches have been compared. These turbulence-modeling methods were employed to simulate a single rotor of a low-speed research compressor featuring a tip clearance of 1.3% of chord length. Comparisons were made between the simulation results and the experimental data at three operating points, and the flow fields at the design point have been specifically discussed in detail. The results show that the advantage of the zonal-LES model becomes obvious as the compressor throttles. The zonal-LES model brings a significant improvement over both the SST model and the SAS model in capturing the experimental data, especially the velocity distribution in the low-span region, as well as the loss near the endwalls. The SAS model as a scale-resolving method presents no benefits in predicting the relevant flow compared with the SST model, as the activation of the SAS source term is limited for this test case. For the loss prediction, the variation in the upper half-span region is mainly due to the different results in modeling turbulent characteristics of the tip leakage flow, whereas the mechanism behind the higher loss at the lower half-span predicted by the zonal-LES model is a consequence of the complex topology of the corner separation and the intensive mixing.

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A hybrid viscous body force model for low-speed centrifugal compressors

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650920944268 ◽

2020 ◽

pp. 095765092094426 ◽

Cited By ~ 1

Author(s):

Zhiyuan Liu ◽

Qingjun Zhao ◽

Xiaorong Xiang ◽

Wei Zhao ◽

Xiaoyong Zhou

Keyword(s):

Body Force ◽

Navier Stokes ◽

Force Model ◽

Tip Leakage Flow ◽

Centrifugal Compressors ◽

Low Speed ◽

Force Method ◽

Body Force Method ◽

Body Forces ◽

Reynolds Averaged Navier Stokes

The flow in centrifugal compressors is viscous and unsteady. Flow separation off the blades challenges the accuracy of simulations. A viscous body force model is expected to speed up numerical convergence and reduce the computational costs of unsteady simulations. In this paper, both stability and accuracy of the viscous body force model are investigated based on the case of a low-speed centrifugal compressor. First, two formulations of the viscous body forces are obtained from the expression of the viscous flux. Then, the numerical stability of two body force models is found to be related to drag coefficient and flow angle. For large negative drag coefficients, the viscous body forces would lead to divergences. Since unsteady Reynolds-averaged Navier–Stokes simulations show that two formulas have considerable accuracy, stability is considered as the main factor for modeling. With the findings, a hybrid viscous body force method is proposed. To assess the applicability of the hybrid model, two test cases are compared against the results obtained by unsteady Reynolds-averaged Navier–Stokes simulations. The first case is the capability evaluation of unsteady characteristics capture for low-speed centrifugal compressors. The simulation results show that the hybrid viscous body force model can capture main unsteady viscous characters, including wake vortexes and tip leakage flow. The other is the case in which the inlet total pressure is disturbed. It is found that fluctuations of pressure, temperature, and velocity predicted by the viscous body force method are close to unsteady Reynolds-averaged Navier–Stokes results. In addition, the time-accurate overall performance of the compressor with disturbance is also predicted satisfactorily. With the advantage in lowering computer resource requirement, the viscous body force model is a promising method for long length scale unsteady cases.

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Hybrid Reynolds-Averaged Navier–Stokes/Large-Eddy Simulations of F-16XL in Low-Speed High-Alpha Flight

Journal of Aircraft ◽

10.2514/1.c034283 ◽

2017 ◽

Vol 54 (6) ◽

pp. 2070-2076 ◽

Cited By ~ 2

Author(s):

Maximilian Tomac ◽

Adam Jirasek ◽

Arthur Rizzi

Keyword(s):

Large Eddy Simulations ◽

Navier Stokes ◽

Low Speed ◽

Large Eddy ◽

Reynolds Averaged Navier Stokes

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Compressible Reynolds-Averaged Navier-Stokes Analysis of Wind Turbine Turbulent Flows Using a Fully-Coupled Low-Speed Preconditioned Multigrid Solver

Volume 3B: Oil and Gas Applications; Organic Rankine Cycle Power Systems; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2014-25562 ◽

2014 ◽

Cited By ~ 2

Author(s):

M. S. Campobasso ◽

M. Yan ◽

J. Drofelnik ◽

A. Piskopakis ◽

M. Caboni

Keyword(s):

Turbulence Model ◽

Static Pressure ◽

Navier Stokes ◽

Acoustic Analogy ◽

Mean Flow ◽

Noise Propagation ◽

Low Speed ◽

Analysis And Design ◽

Reynolds Averaged Navier Stokes ◽

Fully Coupled

The high-fidelity aeromechanical analysis and design of multi-megawatt horizontal axis wind turbines can be performed by means of Reynolds-averaged Navier-Stokes codes. The compressible or incompressible formulation of the fluid equations can be used. One of the objectives of the paper is to quantify the effects of flow compressibility on the aerodynamics of large turbine rotors with particular attention to the tip region of a 82 m rotor blade featuring a relative Mach number of about 0.3 near rated conditions. Noticeable local static pressure variations due to compressibility are observed. Such variations point to the better suitability of compressible solvers for turbine aerodynamics, not only when the solver is used for direct aeroacoustic simulation of the near field noise propagation, but also when it is used to provide the surface static pressure to be used as input for acoustic analogy noise propagation codes. On the numerical side, a novel numerical approach to low-speed preconditioning of the mean flow and turbulence model equations for the fully coupled integration of the flow equations coupled to a two-equation turbulence model is presented and implemented in a compressible Navier-Stokes research code for the steady and yawed wind-induced time-dependent flows analyzed herein.

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