Xiaoling Tong

Bio: Xiaoling Tong is an academic researcher from Mississippi State University. The author has contributed to research in topics: Turbulence & Drag. The author has an hindex of 7, co-authored 13 publications receiving 155 citations.

Comprehensive Numerical Study of Jet-Flow Impingement over Flat Plates

Abstract: Thepresentstudyattemptsanumericalinvestigationofthecomplexe owe eldthatoccurswhenanunderexpanded jet collides against a solid surface. Numerous examples of this problem can be found in the aerospace industry (e.g., rocket test stands, multistage separation ). A simplie ed geometry, already employed in previous experimental inquiries, was chosen as a test case: an underexpanded, axisymmetric, air jet impinging on a e at plate at varied angles. The three-dimensional Navier ‐Stokes equations were solved by means of a second-order-accurate Roetype algorithm with a generalized grid formulation. The computational domain includes theconvergent ‐divergent nozzle and the external e eld. The numerical results show various jet-shock and shock-shock interactions and compare very well with experimental data, including shadowgraph pictures and both location and values of the peak pressures on the inclined plate. This investigation focused on performing a thorough comparison between experiments and simulations, thereby establishing some level of cone dence in the accuracy and reliability of the numerical tool developed, CHEM. CHEM can accommodate more complicated and realistic geometries and physical conditions than those encountered in this study: with further ree nement and validation it can be used for rocket plume and plume/solid surface interaction simulations, both on the ground and in e ight.

Turbulence Models and Heat Transfer in Nozzle Flows

Abstract: Introduction S IGNIFICANT resources have been spent on creating accurate and robust turbulence models for flows with adverse pressure gradients. Capturing correct boundary-layer profiles under adverse pressure gradients is of particular importance to the accurate modeling of separated flows. In favorable pressure-gradient flows, smallscale features of boundary layers generally do not couple to largerscale flow features such as flow separations. As a result, problems that can occur in regions of favorable pressure gradients are more difficult to spot in standard benchmarks. However, accurate modeling of such flows will be required for reliable predictions of surface heat fluxes or shear stresses. Here we investigate the performance of Menter’s two equation shear-stress-transport (SST) turbulence model1 for heat-transfer computation under strongly favorable pressure gradients found in choked nozzle flows (such as required in rocket nozzle analysis and design). We have observed anomalous behavior of the SST turbulence model for strongly favorable pressure-gradient flows. We shall demonstrate the anomaly using an experimental choked nozzle problem published in the open literature.2 The anomaly in the computed heat transfer appears to be caused by the shear-stress-transport correction term of Menter’s model. By design, this term should be active in near-wall regions under adverse pressure gradients. However, it also appears to incorrectly become active under strongly favorable pressure-gradient conditions.

Discrete Surface Evolution and Mesh Deformation for Aircraft Icing Applications

Abstract: Robust, automated mesh generation for problems with deforming geometries, such as ice accreting on aerodynamic surfaces, remains a challenging problem. Here we describe a technique to deform a discrete surface as it evolves due to the accretion of ice. The surface evolution algorithm is based on a smoothed, face-offsetting approach. We also describe a fast algebraic technique to propagate the computed surface deformations into the surrounding volume mesh while maintaining geometric mesh quality. Preliminary results presented here demonstrate the ecacy of the approach for a sphere with a prescribed accretion rate, a rime ice accretion, and a more complex glaze ice accretion.

Loci: a rule-based framework for parallel multi-disciplinary simulation synthesis

Abstract: We present a rule-based framework for the development of scalable parallel high performance simulations for a broad class of scientific applications (with particular emphasis on continuum mechanics). We take a pragmatic approach to our programming abstractions by implementing structures that are used frequently and have common high performance implementations on distributed memory architectures. The resulting framework borrows heavily from rule-based systems for relational database models, however limiting the scope to those parts that have obvious high performance implementation. Using our approach, we demonstrate predictable performance behavior and efficient utilization of large scale distributed memory architectures on problems of significant complexity involving multiple disciplines.

Coupling Heat Transfer and Fluid Flow Solvers for Multidisciplinary Simulations

Abstract: The feasibility of multidisciplinary simulations for realistic geometries involving detailed physical models is demonstrated. Specifically, a three-dimensional chemically reacting fluid flow solver is coupled with a solid-phase heat transfer solver that includes cooling channels. Both fluid- and solid-phase models employ the integral, conservative form of the governing equations and are discretized by means of two finite volume numerical schemes. To keep the heat flux consistent, a special algorithm is developed at the interface between the solid and fluid regions. Physical and thermal properties of the solid materials can be temperature dependent, and different materials can be used in different parts of the domains due to a multiblock gridding strategy. The cooling channel model is developed by using conservation laws of mass, momentum, and energy, taking into account the effects of heat transfer and friction. The coupling of the models (solid and fluid, solid and cooling channels) is detailed. A hot-air nozzle test case is examined

Wall Function Boundary Conditions Including Heat Transfer and Compressibility

Abstract: Wall function boundary conditions that include the effects of compressibility and heat transfer are developed for transport-type turbulence models. The wall functions are based on coupled velocity and temperature profiles valid in both the viscous sublayer and the log layer. The wall function boundary conditions are developed within a rigid set of assumptions so that a consistent set of relationships are derived for the wall shear stress, the wall heat transfer, and the turbulence quantities at the first point off the wall. The new boundary conditions are incorporated into a Navier‐Stokes computational fluid dynamics code that includes the Spalart‐Allmaras and shear stress transport turbulence models. The wall function boundary conditions produce reasonable engineering solutions for the test cases presented for initial wall spacings of y + < 100.