Numerical Predictions of the Performance in Flight of an Air-Breathing Hypersonic Vehicle: HyShot II

2010 ◽  
Author(s):  
Gianluca Iaccarino ◽  
Rene Pec´nik ◽  
Vincent Terrapon ◽  
Alireza Doostan
Keyword(s):  
Free Stream ◽  
Flight Test ◽  
Operating Conditions ◽  
Order Model ◽  
Data Set ◽  
Reduced Order ◽  
Scramjet Combustor ◽  
Numerical Predictions ◽  
Combustion Processes ◽  
Release Model

The uncertainties inherent to the operating conditions of the Hyshot II scramjet flight test are assessed. In particular, the variability of the pressure prediction in the combustor due to uncertain free stream conditions is investigated using a probabilistic methodology based on stochastic collocation. The uncertainties in Mach number, angle of attack and flight altitude are inferred from pressure measurements in the unfueled combustor using a Bayesian inversion approach. The forward computation relies on a reduced order model that represents the combustion processes in the scramjet combustor. A ground based experimental data set obtained from 1-to-1 model of the HyShot II vehicle with well defined operating conditions is used to validate the non-reacting solver and to calibrate the heat release model for the reacting combustor. The model prediction agrees well with the experimentally aquired flight data. On the other hand, our estimated flight free stream conditions differ from previously published results.

New Swash Plate Damping Model for Hydraulic Axial-Piston Pump

1999 ◽  
Vol 123 (3) ◽  
pp. 463-470 ◽  
Author(s):  
X. Zhang ◽  
J. Cho ◽  
S. S. Nair ◽  
N. D. Manring
Keyword(s):  
Open Loop ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Order Model ◽  
Nonlinear Simulation ◽  
Reduced Order ◽  
Swash Plate ◽  
Axial Piston

A new, open-loop, reduced order model is proposed for the swash plate dynamics of an axial piston pump. The difference from previous reduced order models is the modeling of a damping mechanism not reported previously in the literature. An analytical expression for the damping mechanism is derived. The proposed reduced order model is validated by comparing with a complete nonlinear simulation of the pump dynamics over the entire range of operating conditions.

Prediction of Geometrically Induced Localization Effects Using a Subset of Nominal System Modes

2019 ◽  
Author(s):  
Thomas Maywald ◽  
Christoph R. Heinrich ◽  
Arnold Kühhorn ◽  
Sven Schrape ◽  
Thomas Backhaus
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Reduced Order Model ◽  
Vibration Measurement ◽  
Mode Shapes ◽  
Compressor Stage ◽  
Order Model ◽  
Reduced Order ◽  
Numerical Predictions

Abstract It is widely known that the vibration characteristics of blade integrated discs can dramatically change in the presence of manufacturing tolerances and wear. In this context, an increasing number of publications discuss the influence of the geometrical variability of blades on phenomena like frequency splitting and mode localization. This contribution is investigating the validity of a stiffness modified reduced order model for predicting the modal parameters of a geometrically mistuned compressor stage. In detail, the natural frequencies and mode shapes, as well as the corresponding mistuning patterns, are experimentally determined for an exemplary rotor. Furthermore, a blue light fringe projector is used to identify the geometrical differences between the actual rotor and the nominal blisk design. With the help of these digitization results, a realistic finite element model of the whole compressor stage is generated. Beyond that, a reduced order model is implemented based on the nominal design intention. Finally, the numerical predictions of the geometrically updated finite element model and the stiffness modified reduced order model are compared to the vibration measurement results. The investigation is completed by pointing out the benefits and limitations of the SNM-approach in the context of geometrically induced mistuning effects.

scholarly journals In-Situ Residual Tracking in Reduced Order Modelling

2002 ◽  
Vol 9 (3) ◽  
pp. 105-121 ◽  
Author(s):  
Joseph C. Slater ◽  
Chris L. Pettit ◽  
Philip S. Beran
Keyword(s):  
Evaluation Method ◽  
Operating Conditions ◽  
Further Training ◽  
Order Model ◽  
Reduced Order ◽  
Weighted Residuals ◽  
Reduced Order Modelling ◽  
Estimate Error ◽  
Proper Orthogonal

Proper orthogonal decomposition (POD) based reduced-order modelling is demonstrated to be a weighted residual technique similar to Galerkin's method. Estimates of weighted residuals of neglected modes are used to determine relative importance of neglected modes to the model. The cumulative effects of neglected modes can be used to estimate error in the reduced order model. Thus, once the snapshots have been obtained under prescribed training conditions, the need to perform full-order simulations for comparison is eliminates. This has the potential to allow the analyst to initiate further training when the reduced modes are no longer sufficient to accurately represent the predominant phenomenon of interest. The response of a fluid moving at Mach 1.2 above a panel to a forced localized oscillation of the panel at and away from the training operating conditions is used to demonstrate the evaluation method.

Air Entrainment During Steady-State Web Winding

1997 ◽  
Vol 64 (4) ◽  
pp. 916-922 ◽  
Author(s):  
M. B. Keshavan ◽  
J. A. Wickert
Keyword(s):  
Steady State ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Order Model ◽  
Reduced Order ◽  
Pressure Profiles ◽  
Air Layers ◽  
Entrained Air ◽  
Air Film

As a web is wound at speed onto a roll, a thin layer of air becomes entrapped between it and the incoming web stream. The resulting spiral-shaped air bearing separates adjacent web layers and can extend many wraps into the roll. The air entrained during the winding process increases the propensity for lateral interlayer slippage and damage to the edges of the web. In the present paper, an in situ technique is developed for measuring the thickness of the entrained air film during winding, and parameter studies quantify the effects of such winding variables as tension, width, transport speed, and surface roughness. With a view towards evaluating different transport designs and operating conditions, three measures of air entrainment are discussed: (i) the cumulative thickness of all air layers, (ii) the thickness of the outermost air layer at the nip, and (iii) the rate at which air bleeds from the roll once it comes to rest. Measured values of the first two metrics are compared with those predicted by a derived two-dimensional reduced-order model for steady-state winding. The analysis treats the two bounding configurations of symmetric and asymmetric stacking of web layers by specifying appropriate cross-web pressure profiles.

Experimental Investigation on the Loss Production Mechanisms in Transitional Boundary Layers

2020 ◽  
Author(s):  
M. Dellacasagrande ◽  
D. Lengani ◽  
D. Simoni ◽  
M. Ubaldi ◽  
P. Zunino
Keyword(s):  
Boundary Layer ◽  
Strain Rate ◽  
Boundary Layers ◽  
Separated Flow ◽  
Reduced Order Model ◽  
Mean Flow ◽  
Order Model ◽  
Data Set ◽  
Reduced Order ◽  
Stress Tensors

Abstract The present paper discusses the results of a large experimental data set describing transitional boundary layers. Time resolved Particle Image Velocimetry (PIV) measurements have been adopted to survey the boundary layer developing over a flat plate under prescribed adverse pressure gradients typical of turbomachinery components. The tests have been performed while varying the pressure gradient, the Reynolds number and the inlet free-stream turbulence intensity (FSTI). Two exemplary cases, referring to bypass and separated flow transition, are discussed by means of principal axis analysis and proper orthogonal decomposition (POD). The POD is used to provide statistical representation of the flow structures and to compute the turbulence production (i.e., the mean flow energy dissipation) due to the dynamical features observed for the different transition types. Reduced order model representations of the flow field are provided and their contribution to the total turbulence kinetic energy production is isolated. This analysis is closed by the inspection of the eigenvectors of the strain rate and Reynolds stress tensors. For the separated flow case, it is shown that the eigenvectors of strain rate and shear tensor are almost perfectly aligned downstream of the maximum displacement of the bubble. The reduced order model reconstruction of the Kelvin-Helmholtz shed vortices provides the largest part of the overall TKE production. For the high FSTI induced transition, the eigenvectors of the shear and stress tensors do not have the same direction. The loss generation is related to the local maximum Reynolds normal stress in the streamwise direction, induced by the boundary layer streaks and their breakdown.

Solenoid Damping of the Pilot Poppet in a Forced-Feedback Metering Poppet Valve

2007 ◽  
Author(s):  
C. Harvey O. Cline ◽  
Roger Fales
Keyword(s):  
Dynamic Response ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
The Self ◽  
Hydraulic Fluid ◽  
Order Model ◽  
Reduced Order ◽  
Poppet Valve ◽  
Spool Valves ◽  
Poppet Valves

Forced-feedback metering poppet valves offer several advantages over spool valves as metering elements in hydraulic circuits. Despite these advantages, dynamic instabilities in their performance could limit their acceptance in this role. The pilot poppet damping is a source of uncertainty in dynamic response at certain operating conditions. Presently, in the forced-feedback metering poppet valve, the pilot poppet is damped by the flow of hydraulic fluid through a channel or orifice running through the poppet. Here, it is proposed that the solenoid be used to provide damping to the pilot poppet. The damping input to the solenoid is determined using the pilot poppet velocity. In practice, this is a readily unavailable variable and is estimated according to the self-sensing actuator concept. The proposed damping method is developed and analyzed in simulations. Simulations development and analysis occurred via a simplified, reduced order model of the pilot poppet stage.

scholarly journals Validating a Reduced-Order Model for Synthetic Jet Actuators Using CFD and Experimental Data

Actuators ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 67 ◽  
Author(s):  
Tim Persoons ◽  
Rick Cressall ◽  
Sajad Alimohammadi
Keyword(s):  
Synthetic Jet ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
Driving Voltage ◽  
Cavity Pressure ◽  
Order Model ◽  
Reduced Order ◽  
Synthetic Jet Actuators ◽  
Jet Actuators ◽  
Jet Velocity

Synthetic jet actuators (SJA) are emerging in various engineering applications, from flow separation and noise control in aviation to thermal management of electronics. A SJA oscillates a flexible membrane inside a cavity connected to a nozzle producing vortices. A complex interaction between the cavity pressure field and the driving electronics can make it difficult to predict performance. A reduced-order model (ROM) has been developed to predict the performance of SJAs. This paper applies this model to a canonical configuration with applications in flow control and electronics cooling, consisting of a single SJA with a rectangular orifice, emanating perpendicular to the surface. The practical implementation of the ROM to estimate the relationship between cavity pressure and jet velocity, jet velocity and diaphragm deflection and applied driving voltage is explained in detail. Unsteady Reynolds-averaged Navier Stokes computational fluid dynamics (CFD) simulations are used to assess the reliability of the reduced-order model. The CFD model itself has been validated with experimental measurements. The effect of orifice aspect ratio on the ROM parameters has been discussed. Findings indicate that the ROM is capable of predicting the SJA performance for a wide range of operating conditions (in terms of frequency and amplitude).

scholarly journals An Object-Oriented R744 Two-Phase Ejector Reduced-Order Model for Dynamic Simulations

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1282
Author(s):  
Michal Haida ◽  
Rafal Fingas ◽  
Wojciech Szwajnoch ◽  
Jacek Smolka ◽  
Michal Palacz ◽  
...  
Keyword(s):  
Dynamic Simulation ◽  
Object Oriented ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
Refrigeration System ◽  
Order Model ◽  
Two Phase ◽  
Dynamic Simulations ◽  
Climate Zones ◽  
Reduced Order

The object-oriented two-phase ejector hybrid reduced-order model (ROM) was developed for dynamic simulation of the R744 refrigeration system. OpenModelica software was used to evaluate the system’s performance. Moreover, the hybrid ROM results were compared to the results given by the non-dimensional and one-dimensional mathematical approaches of the R744 two-phase ejector. Accuracy of all three ejector models was defined through a validation procedure for the experimental results. Finally, the dynamic simulation of the hybrid ROM ejector model integrated with the R744 refrigeration system was presented based on the summer campaign at three different climate zones: Mediterranean, South American and South Asian. The hybrid ROM obtained the best prediction of ejector mass flow rates as compared with other ejector models under subcritical and transcritical operating conditions. The dynamic simulations of the R744 ejector-based system indicated the ejector efficiency variations and the best efficiency at the investigated climate zones. The coefficient of performance (COP) varied from 2.5 to 4.0 according to different ambient conditions. The pressure ratio of 1.15 allowed a more stabilised system during the test campaign with an ejector efficiency from 20% to over 30%.

A Reduced-Order Model for an Oscillating Hydrofoil Near the Free Surface

2015 ◽  
Author(s):  
Rory C. Kennedy ◽  
Dillon Helfers ◽  
Yin Lu Young
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Equations Of Motion ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
Order Model ◽  
Disturbing Force ◽  
Reduced Order ◽  
Resonance Frequencies ◽  
Force Components

The first objective of this work is to numerically investigate how the proximity to the free surface influences the hydrodynamic response and susceptibility to cavitation of a hydrofoil undergoing controlled pitching oscillations, for high-speed full-scale operating conditions. A second objective is to develop a time-domain Reduced Order Model (ROM) to predict the unsteady hydrodynamic loads (for rapid exploration of the design space and for real-time active/passive actuation/control). The ROM delineates the fluid-structure interaction (FSI) forces into fluid inertial, damping, and disturbing force components, and only predicts the primary oscillation frequency. In addition to predicting the unsteady loads, when coupled with the solid equations of motion, the ROM can also be used to calculate the natural resonance frequencies and damping characteristics with consideration for viscous and free surface effects. This will allow designers to better predict and control the dynamic response of lifting surfaces operating near the free surface.

Design and Experimental Verification of Mistuning of a Supersonic Turbine Blisk

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Pieter Groth ◽  
Hans Mårtensson ◽  
Clas Andersson
Keyword(s):  
Operating Conditions ◽  
Test Rig ◽  
Order Model ◽  
Unstable Region ◽  
Reduced Order ◽  
Flutter Boundary ◽  
Turbine Blisk ◽  
Random Patterns ◽  
System Mode

A rotor blisk of a supersonic space turbine has previously been designed to allow for free flutter to occur in an air test rig (Groth Mårtensson, and Edin, 2010, “Experimental and Computational Fluid Dynamics Based Determination of Flutter Limits in Supersonic Space Turbines,” 132(1), p. 011010). Flutter occurred at several operating conditions, and the flutter boundary for the test turbine was established. In this paper the rotor blisk is redesigned in order to inhibit flutter. The design strategy chosen is to introduce a mistuning concept. Based on aeroelastic analyses using a reduced order model a criterion for the required level of mistuning is established in order to stabilize the lower system modes. Proposals in literature suggest and analyze mistuning by varying blade mode frequencies in random patterns or by modifying blades in an odd-even pattern. Here a modification of sectors of the blisk is introduced in order to bring a sufficient split of the system mode frequencies. To verify that the redesigned blisk efficiently could inhibit flutter, an experiment similar to that in the work of Groth et al. is performed with the mistuned rotor blisk. By running the redesigned blisk at operating conditions deep into the unstable region of the tuned blisk, it is demonstrated that a relative low level of mistuning is sufficient to eliminate rotor flutter.

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