A scalable paradigm is developed to generate 2D/3D high quality finite/spectral element meshes containing arbitrarily curved elements. The current methodology begins with a linear mesh that is decomposed using a graph partitioning scheme. Higher-order elements are then created from the linear mesh, where a CAD model must be queried in order for the curved faces/edges to conform to the boundaries. Subsequently, the curved elements are directly generated using analytical maps which transform the point distribution of the master element to the element in physical space. These analytic maps are derived for triangular, quadrilateral, tetrahedral, prismatic, pyramidal, and hexahedral elements. It is shown that the stretching of Chebyshev/Fekete point distributions are also preserved by these maps and hence they can be used to generate well-conditioned spectral element grids. Since these maps require a computationally intensive min-distance projection to the CAD model, a fast min-distance search algorithm is proposed. The current method is embarrassingly parallel, uses MPI, and is implemented on a commodity cluster. Degradation in performance is observed with load balancing based on maximizing the volume to surface ratio and, therefore, a new load balancing is proposed to mitigate this loss in speed-up. Results are presented for a two-dimensional cylinder, NACA0012 airfoil, 30P30N high-lift geometry, a three-dimensional sphere, a notional missile configuration and a civil aircraft geometry.

To alleviate the damages on launch tube surface from high temperature the rocket exhaust gas during firing the missile, we thus propose the heat transfer enhancement mechanism for the tube wrapped with metal sheet providing the small space, so-called air gap. The idea of the augmentation is by creating the free convection flow pattern in the narrow gap making by wrapping the metal sheet around the launch tube. In this present work, design of experiment is applied to parametrically design the launch tube with metal cover sheet configuration (cylindrical annulus with fins). The objective is to parametrically design and investigate the configuration of the metal-sheet-wrapped launcher. To predict the free convection in narrow cylindrical annulus heated from the below surface (launch tube) including the rotating effect, the CFD investigation of the time-variant axissymmetric flow is conducted. The influences of three design factors, diameter and position of exit channels and air gap thickness on the flow field and the heat transfer are investigated.

RANS models are required for the prediction of scalar fluctuations and turbulent transport in the high speed flow regime. These models will have application, for example, in missile exhaust plume signature analyses, scramjet combustors and other important areas. However, experimentally derived scalar fluctuation data needed to develop these models for the high speed flow regime is not readily available due to the inability of relevant experimental measurement techniques (e.g. hot wires) to cope with this flowfield environment. This issue poses significant difficulties for model development in this flow regime. Researchers have used different values for the turbulent Prandtl and Schmidt numbers but no consensus has been reached as to what these values have to be for high speed flows. To address this difficulty, a two part program has been initiated to fill the data gap and thus facilitate model development. Part I of this program involves the collection of LES data over a wide range of conditions. Part II involves the use of these data to evaluate and develop RANS tools to improve predictive capabilities. This paper presents results and findings of Part I of this program. Several flow fields of relevance to the problems mentioned above are studied. These include classical unit problems such as high and low Mach number shear layers, boundary layers and separated flows such as compression corner flows. In the process we are gradually extending the applicability of LES to more complex flows and at the same time enabling RANS model development by facilitating flow databases in the high speed flight regime. The findings of this study elucidate the effects of compressibility on the character of mean scalar profiles, variations in turbulent Prandtl number, and on scalar rms fluctuations.

Recent activities at CRAFT Tech related to the simulation of high speed laboratory jets, their control via passive actuation, and the scale-up and revisions required for real engines and operation at flight are discussed. We focus on aircraft applications related to jet noise reduction with activities pertinent to varied missile jet/plume applications the subject of other review papers. Laboratory jet experiments have served to validate the RANS turbulence models utilized and are supplemented by LES studies to provide data sets not readily obtainable in the laboratory such as temperature fluctuation data needed for thermal transport modeling. Applications for a military fighter aircraft indicate that laboratory experiments cannot replicate the real exhaust environment and thus can only suggest actuation concepts that are promising. CFD is required to revise and scale-up these concepts for the real engine and to provide estimates of their performance in flight. Studies presented show the differences between laboratory plumes and real plumes, as well as the effects of plume/plume and plume/aerodynamic interactions which are quite appreciable and show a markedly different structure than that of the isolated jet under the same operating conditions.

Classical hydrodynamic force estimation methods are widely used by industrial designers of underwater vehicles for whom captive model experiments and CFD based simulations are uneconomical. They are also used in the preliminary design of submarines and when real time submarine simulations are required. These methods poorly estimate the contribution of the hull to the forces, especially at moderate to high incidence angles. This paper critically reviews the classical hull force estimation methods developed by Munk, Allen, Perkins and Jorgensen, and Sarpkaya. It compares the methods with experimentally validated CFD predictions of a streamlined body at incidence angles up to 30 degrees and for Reynolds numbers from 2.3 to 230 million. The comparison shows that inadequately modeled flow separation and leeside body vortices explain the poor force and moment predictions. This is partly due, at least, to the lack of a streamlined tail on the truncated missile shapes for which the estimation methods were developed.

In this work, numerical simulation is used to study the stability enhancement of high speed supercavitating Shkval missile. Although supercavitation is known as one of the most effective methods for drag reduction, producing the cavity, either by ventilation or by cavitator at front of the body, may cause some instabilities on cavity surface and thus on the projectile’s motion. Therefore removing these instabilities comes as an important point of discussion. First of all, we calculate the sources of instabilities and measure respective forces and then present some approaches that significantly reduce these instabilities. One of these methods that could produce more stable supercavities is injecting of the air into the cavity unsteadily which varies through the projectile’s surface. This approach is provided by arrays of slots distributed on the projectile’s surface and unsteady injection is modeled over the surface. Furthermore, the position of ventilation, dramatically affects the stability like those in aerodynamics. In all approaches it is assumed that the supercavity covers the whole of the body, however the forces caused by the wakes, formed behind the body are taken into account. The calculation is performed at three cavitation numbers with respective velocities of 100 m/s, 150 m/s, 200 m/s.