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Man Long Wong

Publications and source records attributed to Man Long Wong.

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Numerical Study on the Aerodynamics of an Iced Airfoil With Scale-Resolving Simulations

Scale-resolving simulations of the NACA 23012 airfoil with horn ice accretion on the leading edge are conducted using the hybrid Reynolds-averaged Navier–Stokes/large-eddy simulation (hybrid RANS/LES) and wall-modeled large-eddy simulation (WMLES) approaches implemented in the Launch, Ascent, and Vehicle Aerodynamics (LAVA) framework. Aerodynamic results at the Reynolds number of 1.8 million show good comparison with the experimental measurements at different angles of attack from pre-stall to post-stall regimes. The pressure plateaus caused by the flow separation and the recovery of pressure inside the separation bubble around the iced leading edge are well predicted with the scale-resolving simulations when sufficient grid resolution is used around the accreted ice. The unsteadiness of the turbulent flows around the iced airfoil is also examined through the turbulent kinetic energy with the Reynolds normal stress anisotropy. Kelvin–Helmholtz instability (KHI) arises at the shear layer triggered by the upper ice horn and leads to rapid laminar-to-turbulent transition over a large range of angle of attack. With the increase of the angle of attack, the region with high turbulence intensity induced by the unstable shear layer spreads quickly over the entire upper surface of the airfoil. The coherent KHI modes from the upper and lower ice horns are extracted using the spectral proper orthogonal decomposition (SPOD) technique. The SPOD modes extracted from the upper shear layer have large-scale variations in the spanwise direction and low-rank behavior where the energy of the leading SPOD mode at each Strouhal number of the KHI largely represents the total energy when the mode number in the spanwise direction is small.

ARMD↗
NASA NTRSDate not supplied

Predictions of LAGOON Nose Landing Gear Flow and Noise Using Wall-Modeled Large-Eddy Simulations

Wall-modeled large-eddy simulations (WMLESs) of the LAGOON nose landing gear are conducted with compressible Navier–Stokes equations and immersed boundary technique using the Launch, Ascent, and Vehicle Aerodynamics (LAVA) framework. The simulations are conducted using six different Cartesian octree meshes for the grid sensitivity analysis of the near-field and far-field numerical predictions, where the far-field noise results are computed with the Ffowcs Williams–Hawkings acoustic analogy. The effects of numerical tripping induced at the exact locations of the tripping devices in the experiments are also examined. In general, better comparison with the experimental results are shown for the the near-field results obtained with the simulations under the effects of numerical tripping. The effects of tripping are not significant on the far-field noise calculations and the results have reasonable comparison with the experimental data in the low and medium frequency ranges when an impermeable formulation of the acoustic analogy is used.

CST↗
NASA NTRSDate not supplied

Predicting SLS Launch Environment using a Novel Multiphase Formulation

Powerful acoustic waves generated during ignition of launch vehicles may be dangerous to the vehicle, its payload, or the surrounding structures. The water-based Ignition Overpressure and Sound Suppression (IOP/SS) system at Kennedy Space Center’s (KSC) Launch Complex 39B (LC-39B) will be used to protect the Space Launch System (SLS) from the acoustic vibrations generated during launch. The IOP/SS system uses enormous amounts of water to dampen and attenuate these sound waves. To better understand the launch environment risks and to study the effectiveness of the IOP/SS system it is desirable to have time-accurate unsteady simulations of the vehicle ignition with water-based sound suppression. This paper presents results obtained with a novel, high-order accurate, and robust numerical method designed for simulating compressible multiphase flows. A positivity-preserving finite difference scheme is utilized which is formally high-order accurate and also provably robust. Robustness is critical due to the extreme nature of the flow which exhibits highly nonlinear shock and rarefaction waves interacting with liquid-gas interfaces with density ratios of the order of 1000:1. Furthermore, the high-order accuracy (and the high resolution property) is desirable for predicting wave phenomena like IOP waves since the signal can be resolved accurately and propagated long distances with fewer grid points. This finite-difference method was developed using NASA’s Launch, Ascent, and Vehicle Aerodynamics (LAVA) Cartesian immersed boundary framework. We present a validation case by applying our solver to the SLS Scale Model Acoustic Test (SMAT). The SLS SMAT is a well-instrumented 5% scale model test meant to represent the SLS at NASA KSC’s LC-39B pad. Scale IOP tests were performed with and without the sound suppression water and included many sensors which recorded the pressure waves produced during ignition. For this validation case we conduct two simulations, likewise with and without sound suppression water, and compare the SLS SMAT pressure sensor signals with our numerical signals at identical locations. Following this validation case we present a study of the SLS launch environment to examine engineering safety concerns about the mobile launch pad. Engineers at KSC redesigned the main flame deflector at LC-39B anticipating the increased loads from the SLS and to repair damage from prior Shuttle missions. This deflector redesign made use of surface pressure and temperature data from LAVA full-scale SLS simulations without the sound suppression system. The engineers were questioning the possibility of increased pressure loads on the underside of the mobile launcher due to the water in the flame trench. Based on the results established in our simulations of the SLS SMAT, we performed updated calculations for SLS at LC-39B with and without water systems active to assess the readiness of the launch pad for Artemis I launch. Our results show that the IOP/SS system is effective at reducing the overpressure signal and overall sound pressure levels felt by the vehicle and additionally that the pressure loads experienced by the mobile launcher (ML) during engine startup is not increased by the presence of water.

EGS↗