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Freestream

About: Freestream is a research topic. Over the lifetime, 3428 publications have been published within this topic receiving 56147 citations.


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Proceedings ArticleDOI
05 Jan 2015
TL;DR: In this article, a grid resolution study is presented in which the resolution required to resolve the flow within a supersonic cavity flameholder is determined, based on a series of experiments for which particle image velocimetry measurements of two velocity components were made within the cavity.
Abstract: Simulation results are presented for non-reacting flow within a supersonic cavity flameholder. The freestream is air at Mach 2. A case is simulated with no fuel injection and with ethylene fuel injected through holes located on the back face of the cavity. The simulations correspond to a series of experiments for which particle image velocimetry measurements of two velocity components were made within the cavity. The flow within the cavity is computed using unsteady hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation. A thorough grid resolution study is presented in which the resolution required to resolve the flow within the cavity is determined. The influence of the level of turbulence within the oncoming boundary layer is examined and found to significantly affect the velocity field and mixing within the cavity. The effect of the side walls is investigated by comparing simulations of the full-width duct to simulations of a partial-width duct that uses periodic boundary conditions. Differences in resolved turbulence kinetic energy and mixing are seen between the full-width and partial width simulations. The results of the simulations are also compared to the velocity measurements from the experiments, and the hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation results are found to compare reasonably well with the experiment in most locations. Improved agreement with fluctuating velocity components is found when the simulation results are filtered to a resolution corresponding to the resolution of the velocity measurement technique.

18 citations

Journal ArticleDOI
TL;DR: In this paper, a numerical simulation of transient hypersonic flows involving shock-wave-freestream-disturbance interactions is presented using the essentially nonoscillatory (ENO) schemes.
Abstract: Numerical simulation of transient hypersonic flows involving shock-wave-freestream-disturbance interactions is presented using the essentially nonoscillatory (ENO) schemes. The ENO schemes were chosen for transient-flow simulations because they have high-order accuracy at extrema as well as in other parts of smooth solutions. First, the accuracy of the ENO schemes was tested numerically by applying them to the computations of a one-dimensional linear model equation and to an oscillating plate problem using the two-dimensional Navier-Stokes equations. Then, the third-order ENO scheme was used to compute the unsteady interaction of a freestream acoustic wave with a bow shock in hypersonic flow past a cylinder. The numerical results along the stagnation line were compared with linearized analytical solutions. The results show that the disturbance waves generated behind the bow shock are significantly amplified by the back-and-forth interactions and reflections of the acoustic waves. These results on the bow-shock-disturbance interactions will be useful in understanding the effects of the bow shock wave on the receptivity of hypersonic boundary layers to freestream disturbances.

18 citations

Proceedings ArticleDOI
05 Jan 2015
TL;DR: In this article, a 2:1 elliptic cone model was tested in a variable-Mach-number conventional hypersonic wind tunnel and the effect of the freestream pressure and noise on measured disturbances was investigated.
Abstract: A 2:1 elliptic cone model was tested in a variable-Mach-number conventional hypersonic wind tunnel. Freestream Reynolds number, Mach number, model streamwise location, and model wall temperature were all varied to ascertain the effect of each on measured disturbances. A low-frequency disturbance was observed at Mach 5.8. It experienced some growth in excess of the increasing freestream pressure and noise for a narrow Reynolds number range. Disturbance properties were similar to what was measured in another conventional hypersonic wind tunnel. For Mach 6.5 and 7, there was no evidence of traveling crossflow waves. However, higher-frequency disturbances were observed. These disturbances were nearly two-dimensional and had phase speeds near the expected edge velocity. It is possible that these disturbances were second mode waves. None of the measured disturbances corresponded to any feature of the freestream Pitot spectra.

18 citations

01 Feb 1980
TL;DR: In this article, the effect of aerodynamic interference on the performance of two curved bladed Darrieus-type vertical axis wind turbines has been calculated using a vortex/lifting line aerodynamic model.
Abstract: The effect of aerodynamic interference on the performance of two curved bladed Darrieus-type vertical axis wind turbines has been calculated using a vortex/lifting line aerodynamic model. The turbines have a tower-to-tower separation distance of 1.5 turbine diameters, with the line of turbine centers varying with respect to the ambient wind direction. The effects of freestream turbulence were neglected. For the cases examined, the calculations showed that the downwind turbine power decrement (1) was significant only when the line of turbine centers was coincident with the ambient wind direction, (2) increased with increasing tipspeed ratio, and (3) is due more to induced flow angularities downstream than to speed deficits near the downstream turbine.

17 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023195
2022350
2021108
2020113
201986
2018118