In an effort to reduce cost associated with flight test and certification of new weapon systems/stores for the F-22 Advanced Tactical fighter, Lockheed Martin Aeronautics has conducted a study to assess the capability of several commercial computational fluid dynamics (CFD) codes to predict cavity bay acoustics. Initially a literature survey was conducted to identify commercial, in-house, and research computer codes which have been or are presently being used to simulate cavity flows and the resultant acoustic environment. Four CFD/CAA codes were down-selected for evaluation. Code evaluations were based on comparison of predicted results with experimental data. For this purpose, four wind tunnel test cases based on the V10 1/15-scale F-22 main weapon bay (MWB) model were selected. The cases selected include both subsonic and supersonic test conditions, with both an empty MWB configuration and an inboard stowed AIM-120 configuration. This paper discusses in detail the process, application, and results using the Falcon v4 CFD code which was determined to be the best performer in predicting both subsonic and supersonic TOBSPL frequencies above 100 Hz. Results indicate Falcon v4 predictions compare very favorably for the subsonic test conditions and configurations analyzed, and tends to slightly over predict the response for the supersonic test conditions at some locations. The results of this study have proved favorable enough that correlation using a full scale CFD model with actual F-22 flight test data is proceeding.
TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractUsing adiabatic compression of gas in the pump, a model is shown that can be used to calculate the down-hole pump dynamometer card for various degrees of pump fill of liquids and gas at various degrees of pressure. The load release portion of the card is emphasized. It is shown how the lower pressure gas in the pump promotes what is commonly termed fluid pound or slap and higher pressure gas in the pump promotes what is termed gas interference.The equations that are needed to model these effects for inclusion into wave equation pump models are presented and example calculated pump cards are shown, calculated from wave equation simulations. Since even with so-called fluid pound, gas is first compressed before the plunger encounters the mostly incompressible fluid in the pump, the traveling valve always encounters compressed gas sufficient to open the valve before the plunger "hits" the fluid. This is true as long as gas is in the barrel when incomplete fluid fill occurs. Given this fact, the time step in wave equation solution is examined as the load release in the so called "fluid pound" can happen over a very short time and longer time steps in the wave equation simulation could mask forces from short term forces.The effects of rapid load release on forces in the rods are studied vs. what the forces might be due to the commonly supposed forces from impact with the fluid when "fluid pound" is modeled. Other parameters such as pump fillage, intake pressure and sinker bars are examined for their effects on calculated rod compression
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