Detached-eddy Simulation Predictions Research Articles

Mach 6 Wake Flow Simulations Using a Large-Eddy Simulation/Reynolds-Averaged Navier–Stokes Model

A hybrid large-eddy simulation/Reynolds-averaged Navier–Stokes turbulence model is used to simulate the Mach 6 flow around a scaled model similar to NASA’s Orion multipurpose crew vehicle. The results for surface pressure and heat transfer are compared with experimental data from previous base flow experiments conducted at the Calspan—University at Buffalo Research Center. Using the highest Reynolds number test case ( based on capsule diameter), different numerical aspects of the hybrid approach are addressed, such as use of a low-dissipation scheme, a modification to the eddy-viscosity blending function, time-averaging results, filtering computational results, and sensitivity to grid resolution. In addition, results are compared with Reynolds-Averaged Navier–Stokes using Menter’s two-equation baseline model and to detached-eddy simulation predictions. By introducing a new modification to the blending from Reynolds-averaged Navier–Stokes to large-eddy simulation within boundary layers, very good agreement with the experiment is obtained in regions where the boundary-layer grid spacing is too coarse for large-eddy simulation. The findings show that the high-fidelity schemes produce results that agree much better with the experimental data than Reynolds-averaged Navier–Stokes methods, which tend to underpredict base pressures and overpredict heat fluxes. The overall accuracy of each scheme is evaluated using a normalized root mean square error in different regions of the flow, and the analysis shows that, in separated regions, the integrated error is over 120% using a Reynolds-averaged Navier–Stokes model, and 30–50% using the higher fidelity schemes. Additionally, the hybrid methodology presented is further validated by considering a lower Reynolds number (), where the flow is nominally transitional, and very accurate heat transfer predictions are also obtained.

Hybrid Reynolds-Averaged Navier–Stokes/Large-Eddy Simulation Models for Flow Around an Iced Wing

This study evaluates the feasibility of applying a newly developed dynamic hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation modeling framework to predict the massively separated flow around a GLC-305 airfoil with a 22.5 min leading-edge glaze ice accretion. Three-dimensional numerical simulations were performed at , , and . Comparisons were made between experimental data and simulation results computed using two Reynolds-averaged Navier–Stokes models (Menter’s shear stress transport and Spalart–Allmaras) and two hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation models (delayed detached-eddy simulation and the dynamic hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation model). All models overpredicted the mean wall static pressures on the suction surface. Wall pressure predictions obtained using the Reynolds-averaged Navier–Stokes and dynamic hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation models exhibited qualitatively better agreement with experiments than did delayed detached-eddy simulation predictions, and the dynamic hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation model produced the best agreement for the mean streamwise velocity profiles. Turbulent intensity profiles showed substantial mesh sensitivity for the delayed detached-eddy simulation model simulations, whereas the dynamic hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation model results qualitatively compared well with the experiments and exhibited only a small degree of mesh sensitivity. Unique to the dynamic hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation simulations was the accurate prediction of the flow reattachment location. None of the Reynolds-averaged Navier–Stokes models predicted flow reattachment, and the delayed detached-eddy simulation model predicted a substantially delayed flow reattachment.

Detached-Eddy Simulation Procedure Targeted for Design

A new detached-eddy simulation procedure, MBFLO, is described for the simulation of turbulent flow over/within arbitrary geometry. This new procedure represents the first step toward developing a turbulent technique that reduces the reliance on traditional turbulence modeling by directly solving for the larger-scale turbulence effects in regions where the computational grid is sufficient to resolve those scales. A goal of this effort was to develop a detached-eddy simulation procedure-for which the time-averaged solution can replace current steady simulation results for design. Because detached-eddy simulation requires the solution of the unsteady Navier-Stokes equations on computational grids that are typically an order in magnitude more dense than their Reynolds-averaged counterparts, special care was taken to make this new procedure computationally efficient. This paper describes the data structure, parallelization, and automation techniques used to produce time-averaged detached-eddy simulation predictions. Results for the turbulent flow through a turbine and compressor cascade at design and offdesign conditions, respectively, are shown to illustrate the technique.

Detached-Eddy Simulation Around a Forebody with Rotary Motion

Predictions of the massively separated flow around a rectangular ogive forebody are obtained using detached-eddy simulation and from a solution of the unsteady Reynolds-averaged Navier-Stokes equations. The lengths of the forebody and aftbody are 2 and 4 times the body diameter, respectively. Angles of attack of 60 and 90 deg are considered, the Reynolds number based on freestream speed and diameter is 2.1 x 10 6 , and the freestream Mach number is 0.21. Computations of the static geometry and of the ogive undergoing prescribed rotary motion are performed on a range of meshes with grid refinement from 2.1 x 10 6 to 8.75 x 10 6 cells. flow visualizations of the instantaneous vorticity show that the detached-eddy simulation predictions exhibit an increase in the range of resolved scales with increased mesh resolution. Detached-eddy simulation predictions of the pressure distribution at axial stations along the forebody are in good agreement with measured values for both angles of attack. Unsteady Reynolds-averaged Navier-Stokes predictions of the pressure along the forebody for 90 deg angle of attack exhibit relatively strong coherence, with the resulting pressure variation different from the measured values and detached-eddy simulation results. Detached-eddy simulation predictions of the ogive experiencing rotary motion about its center are obtained for spin coefficients of 0.1 and 0.2 at 90 deg angle of attack. Agreement between the predicted and measured pressure distributions for these cases is less satisfactory compared to the static-geometry results.