Abstract: This report describes an experimental and numerical study of impinging, incompressible, axisymmetric, laminar jets, where the jet axis of symmetry is aligned normal to the wall. Particle Streak Velocimetry (PSV) is used to measure axial velocities along the centerline of the flow field. The jet-nozzle pressure drop is measured simultaneously and determines the Bernoulli velocity. The flowfield is simulated numerically by an axisymmetric Navier-Stokes spectral-element code, an axisymmetric potential-flow model, and an axisymmetric one-dimensional streamfunction approximation. The axisymmetric viscous and potential-flow simulations include the nozzle in the solution domain, allowing nozzle-wall proximity effects to be investigated. Scaling the centerline axial velocity by the Bernoulli velocity collapses the experimental velocity profiles onto a single curve that is independent of the nozzle-plate separation distance. Axisymmetric direct numerical simulations yield good agreement with experiment and confirm the velocity profile scaling. Potential-flow simulations reproduce the collapse of the data, however, viscous effects result in disagreement with experiment. Axisymmetric one-dimensional streamfunction simulations can predict the flow in the stagnation region if the boundary conditions are correctly specified. The scaled axial velocity profiles are well-characterized by an error function with one Reynolds-number dependent parameter. Rescaling the wall-normal distance by the boundary-layer displacement-thickness-corrected diameter yields a collapse of the data onto a single curve that is independent of the Reynolds number. These scalings allow the specification of an analytical expression for the velocity profile of an impinging laminar jet over the Reynolds number range investigated of 200 ≤ Re ≤ 1400.

ID: CaltechGALCITFM:2005.003

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Abstract: Introduction: This annual report describes research accomplishments for FY 99 of the Center for Simulation of Dynamic Response of Materials. The Center is constructing a virtual shock physics facility in which the full three dimensional response of a variety of target materials can be computed for a wide range of compressive, ten- sional, and shear loadings, including those produced by detonation of energetic materials. The goals are to facilitate computation of a variety of experiments in which strong shock and detonation waves are made to impinge on targets consisting of various combinations of materials, compute the subsequent dy- namic response of the target materials, and validate these computations against experimental data.

No.: ASCI-TR033
ID: CaltechASCI:1999.033

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Abstract: Introduction: This annual report describes research accomplishments for FY 98 of the Center for Simulation of Dynamic Response of Materials. The Center is constructing a virtual shock physics facility in which the full three dimensional response of a variety of target materials can be computed for a wide range of compressive, tensional, and shear loadings, including those produced by detonation of energetic materials. The goals are to facilitate computation of a variety of experiments in which strong shock and detonation waves are made to impinge on targets consisting of various combinations of materials, compute the subsequent dynamic response of the target materials, and validate these computations against experimental data.

ID: CaltechASCI:1998.032

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Abstract: Significant progress was made in the third year of an interdisciplinary experimental, numerical and theoretical program to extend the state of knowledge and understanding of the effects of chemical reactions in hypervelocity flows. The program addressed the key problems in aerothermochemistry that arise from.the interaction between the three strongly nonlinear effects: Compressibility; vorticity; and chemistry. Important new results included: • New data on transition in hypervelocity carbon dioxide flows • New method of free-piston shock tunnel operation for lower enthalpy • Accurate new method for computation of self-similar flows • New experimental data on flap-induced separation at high enthalpy • Insight into mechanisms active in reacting shear layers from comparison of experiment and computation • Extensive new data from Rayleigh scattering diagnostics of supersonic shear layer • Comparison of new experiments and computation of hypervelocity double-wedge flow yielded important differences • Further first-principles computations of electron collision cross-sections of CO, N_2 and NO • Good agreement between EFMO computation and experiment of flow over a cone at high incidence • Extension of LITA diagnostics to high temperature.

ID: CaltechAUTHORS:20141111-111211793

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Abstract: A parallel program archetype aids in the development of reliable, efficient parallel applications with common computation/communication structures by providing stepwise refinement methods and code libraries specific to the structure. The methods and libraries help in transforming a sequential program into a parallel program via a sequence of refinement steps that help maintain correctness while refining the program to obtain the appropriate level of granularity for a target machine. The specific archetype discussed here deals with the integration of task and data parallelism by using collective (or group) communication. This archetype has been used to develop several applications.

ID: CaltechCSTR:1994.cs-tr-94-08

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