Back flow from jet plumes in vacuum
Approximate analytical calculations to determine particle density at surrounding points forward of jet nozzle in vacuum due to exhausted gas in jet plume
Grier, N. T.↗
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Back flow from jet plumes in vacuum
Particle density of jet plumes exhausting in vacuum calculated for He, Ar and N
Grier, N. T.↗
Enceladus and Europa: How Does Hydrothermal Activity Begin at the Surface?
The question of how the surface hydrothermal activity (e.g., eruptive plumes and heat flow) is initiated can be addressed within the frame-work of our "Perrier Ocean" model. This model delivers the necessary heat and chemicals to support the heat flow and plumes observed by Cassini in Enceladus' South Polar Region. The model employs closed-loop circulation of water from a sub-surface ocean. The ocean is the main reservoir of heat and chemicals, including dissolved gases. As ocean water moves up toward the surface, pressure is re-duced and gases exsolve forming bubbles. This bub-bly mixture is less dense than the icy crust and the buoyant ocean-water mixture rises toward the surface. Near the surface, heat and chemicals, including some volatiles, are delivered to the chambers in which plumes form and also to shallow reservoirs that keep the surface ice "warm". (Plume operations, per se, are as described by Schmidt et al. and Postberg et al. and are adopted by us.) After transferring heat, the water cools, bubbles contract and dissolve, and the mixture is now relatively dense. It descends through cracks in the crust and returns to the ocean. Once the closed-loop circulation has started it is self-sustaining. Loss of water via the erupting plumes is relatively negligible compared to the amount needed to maintain the heat flow.We note that the activity described herein for the the "Perrier-Ocean" model could, a priori, apply to all small icy bodies that sheltered an interior ocean at some point in their history.
Enceladus↗
Optical Diagnostic Imaging of Multi-Rocket Plume-Induced Base Flow Environments
No abstract available
Mehta, Manish↗
Plume effects on the flow around a blunted cone at hypersonic speeds
Tests at M = 8.2 show that a simulated rocket plume at the base of a blunted cone can cause large areas of separated flow, with dramatic effects on the heat transfer rate distribution. The plume was simulated by solid discs of varying sizes or by an annular jet of gas. Flow over the cone without a plume is fully laminar and attached. Using a large disc, the boundary layer is laminar at separation at the test Reynolds number. Transition occurs along the separated shear layer and the boundary layer quickly becomes turbulent. The reduction in heat transfer associated with a laminar separated region is followed by rising values as transition occurs and the heat transfer rates towards the rear of the cone substantially exceed the values obtained without a plume. With the annular jet or a small disc, separation occurs much further aft, so that heat transfer rates at the front of the cone are comparable with those found without a plume. Downstream of separation the shear layer now remains laminar and the heat transfer rates to the surface are significantly lower than the attached flow values.
Atcliffe, P.↗
A method for simulating 3-D aircraft flow fields with jet plume effects
The objective is to develop, demonstrate, and document a coupled flow analysis procedure for computing 3D aircraft flow fields with deflected subsonic and supersonic jet exhaust plumes. The PNS plume code was transferred to the Ames computer facility for execution on the Cray computer. No problems were encountered when installing this code. The Bower's test case is currently being run. This case is being used to fine tune the procedure for coupling the plume code to PANAIR.
Source record↗
10-kHz Rate Tomographic Rayleigh Scattering Imaging
This presentation gives an overview of tomographic Rayleigh scattering imaging in ground test facilities.
particle image velocimetry↗
Flow Visualization for Plume-Surface Interaction at Martian-Relevant Lander Environments
This paper describes a jet impingement experiment performed in a large-scale vacuum chamber at Martian-relevant ambient pressure conditions, with the motivation of studying plume-surface interaction (PSI) caused by the exhaust plume of a lander interacting with the planetary surface. Flow visualization of an inert supersonic jet was performed using planar laser-induced fluorescence (PLIF), which is a molecular-based, two-dimensional measurement technique. Representative instantaneous and time-averaged visualizations of the impinging jet at two different nozzle flow conditions corresponding to the underexpanded and overexpanded jet regimes are presented for up to six different dimensionless altitudes h/De. The time-averaged measured spatial distribution of impingement pressures at these conditions is also reported. The PLIF visualizations appear to be critical towards explaining unexpected behavior in the impingement pressure, such as a higher impingement pressure for the underexpanded condition at h/De = 10, compared to a lower altitude of h/De = 8. This behavior can be attributed to differences in the stagnation shock structure observed in the PLIF images. The PLIF images also reveal significant flow separation at the nozzle exit for the overexpanded jet conditions. Further analysis of the test data as well as combined flow visualization and surface diagnostics for future ground tests will help inform engineering designs for landings on the Martian surface while mitigating PSI risks.
PLIF↗
Flow Visualization for Plume-Surface Interaction at Martian-Relevant Lander Environments
This paper describes a jet impingement experiment performed in a large-scale vacuum chamber at Martian-relevant ambient pressure conditions, with the motivation of studying plume-surface interaction (PSI) caused by the exhaust plume of a lander interacting with the planetary surface. Flow visualization of an inert supersonic jet was performed using planar laser-induced fluorescence (PLIF), which is a molecular-based, two-dimensional measurement technique. Representative instantaneous and time-averaged visualizations of the impinging jet at two different nozzle flow conditions corresponding to the underexpanded and overexpanded jet regimes are presented for up to six different dimensionless altitudes h/De. The time-averaged measured spatial distribution of impingement pressures at these conditions is also reported. The PLIF visualizations appear to be critical towards explaining unexpected behavior in the impingement pressure, such as a higher impingement pressure for the underexpanded condition at h/De = 10, compared to a lower altitude of h/De = 8. This behavior can be attributed to differences in the stagnation shock structure observed in the PLIF images. The PLIF images also reveal significant flow separation at the nozzle exit for the overexpanded jet conditions. Further analysis of the test data as well as combined flow visualization and surface diagnostics for future ground tests will help inform engineering designs for landings on the Martian surface while mitigating PSI risks.
PLIF↗
Plume characteristics of single-stream and dual-flow conventional and inverted-profile nozzles at equal thrust
The plume velocity and temperature decay rates of single-stream, conventional dual-flow and inverted-profile dual-flow nozzles are compared at equal values of ideal thrust over a wide range of flow conditions. The comparisons are made in terms of constant velocity and temperature contour maps. The results show that both dual-flow nozzle types have much greater plume velocity and temperature decay rates than those of equivalent thrust single-stream nozzles when the respective secondary flows were at ambient temperature. With hot secondary flows, the inverted-profile dual-flow plumes decayed significantly faster than those of single-stream nozzles; however, the decay rates for the conventional dual-flow streams were about the same as those for the single-stream nozzles. Consequently, with hot secondary flows, the inverted-profile dual-flow plumes decayed much faster than the conventional dual-flow plumes at equal thrust.
Vonglahn, U. H.↗
Plume characteristics of single-stream and dual-flow conventional and inverted-profile nozzles at equal thrust
The plume velocity and temperature decay rates of single-stream, conventional dual-flow and inverted-profile dual-flow nozzles are compared at equal values of ideal thrust over a wide range of flow conditions. The comparisons are made in terms of constant velocity and temperature contour maps. The results show that both dual-flow nozzle types have much greater plume velocity and temperature decay rates than those of equivalent thrust single-stream nozzles when the respective secondary flows were at ambient temperature. With hot secondary flows, the inverted-profile dual-flow plumes decayed significantly faster than those of single-stream nozzles; however, the decay rates for the conventional dual-flow streams were about the same as those for the single-stream nozzles. Consequently, with hot secondary flows, the inverted-profile dual-flow plumes decayed much faster than the conventional dual-flow plumes at equal thrust.
Von Glahn, U. H.↗
Towards Understanding the Fluid Dynamic Phenomenon of Interest to Rocket Base Heating: A Review
The significance of the base heating problem for rockets during ascent is due to the complex interaction between the rocket nozzle plumes and the external-flow which can change the flow characteristics in the base region dramatically. At lower altitudes the external-flow merges with the plume-flow, without the formation of a large separated flow region, and the cooler external-flow promotes convective cooling of the base wall. Under these conditions the majority of the base heating is due to radiative heating from the shock heated plume gases. At higher altitudes, however, the process of base heating is not so straightforward. The plume and the base flow expands dramatically and separated flow regions occur in the base area. Hot exhaust gases from the rocket nozzle will be entrained into the separated flow regions and produce a convective component to the base wall heating. Further, if the rocket exhaust-gas contains soot, the soot can increase the emission from the gas and dramatically increase the wall absorption coefficient for radiative heating if it is deposited on the walls . In addition, if the rocket exhaust gas is fuel rich, the fuel can bum in the separated flow regions and further increase the base heating. The base burning phenomenon, and the increased base heating caused by it at higher altitudes, have been observed for the Space Shuttle and Saturn Rocket. Under these conditions, the total heating is significantly higher than the heating without separated flow in the base region, and the increase in heating is directly attributable to the fluid dynamic complexity of the base region. Realistic simulation of the base heating requires that the calculated flow environment reproduce the fluid dynamic flow features accurately. Thus, it will be necessary to introduce into the CFD codes the capability for the flow to respond to the complex vehicle geometry, the effect of turbulence, the ability to accurately reproduce the plume shock/shear layer structures and capture such phenomenon as shock induced base separation and base-burning phenomenon. A survey of experimental, theoretical and computational work that details the fluid dynamics of the base flow environment will be presented in the proposed paper. CFD simulations of rocket base flows using standard CFD codes such as OVERFLOW or GASP will be explored to capture these phenomenon accurately. Merits and limitations of these codes for base flow environment predictions will be explored.
Venkatapathy, E.↗
Flow Visualization of Intrusive and Non-Intrusive Configurations for Lunar- and Martian-Relevant Plume-Surface Interaction
Flow visualization of a heated, inert-gas plume impinging onto a rigid surface was performed in lunar- and Martian-relevant pressure conditions. The experimental campaign was part of a broader effort to improve predictive models and capabilities for plume-surface interactions in spacecraft landing environments relevant to the Moon and Mars. The experiments used the planar laser induced fluorescence (PLIF) technique to visualize the flow of the jet over both a full-plane configuration using a flat impingement plate and a half-plane configuration where the jet flow was bisected by a splitter edge mounted to the impingement plate. The latter configuration has been previously used to study erosion mechanisms in plume-surface interactions because the technique enables cross-sectional optical access for visualizing the plume-induced crater. However, this approach has some uncertainty regarding the influence of the splitter edge on the flow field. The present work evaluates the differences in flow structures and characteristics between the flat plate and splitter plate experimental configurations at eight unique test conditions with and without the splitter edge where the vacuum chamber pressure, nozzle mass flow rate, and height of the nozzle were varied. Several features are identified which differ between the flat plate and splitter plate comparison cases, and these are summarized in this paper. The results presented provide insights to the differences between intrusive and non-intrusive experimental configurations for plume-surface interaction studies that can be used to further validate predictive models and inform future ground and flight test results.
PLIF↗
Flow Visualization of Intrusive and Non-Intrusive Configurations for Lunar- and Martian-Relevant Plume-Surface Interaction
Flow visualization of a heated, inert-gas plume impinging onto a rigid surface was performed in lunar- and Martian-relevant pressure conditions. The experimental campaign was part of a broader effort to improve predictive models and capabilities for plume-surface interactions in spacecraft landing environments relevant to the Moon and Mars. The experiments used the planar laser-induced fluorescence (PLIF) technique to visualize the flow of the jet over both a full-space configuration using a flat impingement plate and a half-space configuration where the jet flow was bisected by a splitter edge mounted to the impingement plate. The latter configuration has been previously used to study erosion mechanisms in plume-surface interactions because the technique enables cross-sectional optical access for visualizing the plume-induced crater. However, this approach has some uncertainty regarding the influence of the splitter edge on the flow field. The present work evaluates the differences in flow structures and characteristics between the flat plate and splitter plate experimental configurations at eight unique test conditions with and without the splitter edge where the vacuum chamber pressure, nozzle mass flow rate, and height of the nozzle were varied. Several features are identified which differ between the flat plate and splitter plate comparison cases, and these are summarized in this paper. The results presented provide insights to the differences between intrusive and non-intrusive experimental configurations for plume-surface interaction studies that can be used to further validate predictive models and inform future ground and flight test results.
PLIF↗
Flow Visualization for Plume-Surface Interaction Testing Within Large-Scale Vacuum Environments at Conditions Relevant to Lunar and Martian Landers
Interactions between rocket exhaust plumes and the landing surface during powered spacecraft descent on the Moon and Mars pose significant risks to the landing vehicle, landing site, and nearby infrastructure. Understanding the underlying plume-surface interaction phenomena through ground test data can provide critical insights on the sensitivities of parameters such as the spacecraft altitude and thrust. In the present work, we summarize a scaled ground test recently conducted within a 20-ft vacuum chamber environment located in the historical East Test Area at the NASA Marshall Space Flight Center. The ground test featured a Mach 5.3 inert gas plume impinging upon an instrumented flat plate. Planar laser-induced fluorescence, which is a 2D laser-based flow field measurement technique, was performed at this test area for the first time to visualize salient flow features such as the barrel shock, stagnation shock, and wall jet. Measurements were obtained at discrete lander altitudes, made dimensionless using the nozzle exit diameter, corresponding to h/D = 10, 8, 5, 4, 3, and 2. The stagnation pressures of the plume were varied from approximately 0.04 to 1 MPa, providing sensitivity to the engine thrust of a powered spacecraft. The unique test facility allowed for near-lunar conditions to be obtained at initial vacuum chamber pressures less than 0.1 Pa. Martian-relevant measurements were also performed at ambient pressures near 600 Pa. Furthermore, a third set of measurements were obtained at so called lunar-relevant conditions near 3 Pa chamber pressure
Plume Surface Interaction↗
Flow Visualization for Plume-Surface Interaction Testing Within Large-Scale Vacuum Environments at Conditions Relevant to Lunar and Martian Landers
Interactions between rocket exhaust plumes and the landing surface during powered spacecraft descent on the Moon and Mars pose significant risks to the landing vehicle, landing site, and nearby infrastructure. Understanding the underlying plume-surface interaction phenomena through ground test data can provide critical insights on the sensitivities of parameters such as the spacecraft altitude and thrust. In the present work, we summarize a scaled ground test recently conducted within a 20-ft vacuum chamber environment located in the historical East Test Area at the NASA Marshall Space Flight Center. The ground test featured a Mach 5.3 inert gas plume impinging upon an instrumented flat plate. Planar laser-induced fluorescence, which is a 2D laser-based flow field measurement technique, was performed at this test area for the first time to visualize salient flow features such as the barrel shock, stagnation shock, and wall jet. Measurements were obtained at discrete lander altitudes, made dimensionless using the nozzle exit diameter, corresponding to h/D = 10, 8, 5, 4, 3, and 2. The stagnation pressures of the plume were varied from approximately 0.04 to 1 MPa, providing sensitivity to the engine thrust of a powered spacecraft. The unique test facility allowed for near-lunar conditions to be obtained at initial vacuum chamber pressures less than 0.1 Pa. Martian-relevant measurements were also performed at ambient pressures near 600 Pa. Furthermore, a third set of measurements were obtained at so called lunar-relevant conditions near 3 Pa chamber pressure.
Plume Surface Interaction↗
On turbulent spots in plane Poiseuille flow
Turbulence characteristics inside a turbulent spot in plume Poiseuille flow are investigated by analyzing a data base obtained from a direct numerical simulation. The spot is found to consist of two distinct regions - a turbulent area and a wave area. The flow inside the turbulent area has a strong resemblance to that found in the fully developed turbulent channel. Suitably defined mean and rms fluctuations as well as the internal shear layer structures are found to be similar to the turbulent counterpart. In the wave area, the inflexional mean spanwise profiles cause a rapid growth of oblique waves, which break down to turbulence. The breakdown process of the oblique waves is reminiscent of the secondary instability observed during transition to turbulence in channel and boundary layer flows. Other detailed characteristics associated with the Poiseuille spot are presented and are compared with experimental results.
Henningson, Dan S.↗
The Kinetic Nonequilibrium Processes in the Internal Flow and in the Plume of Subsonic and Supersonic Aircrafts
(1) Our results show that under combustion of thermal destruction products of n-C8H18, and other hydrocarbon fuels with air at the equivalent ratio -0.5 and less the chemical equilibrium is not realized at the exit plane of combustion chamber and in the gas turbine and nozzle for most of small components such as NO2, NO3, HNO, HNO2, HNO3, N(x)H(y), HO2, OH. The chemical equilibrium is not realized in the internal flow of ramjet hydrogen combustion engine too. So at the nozzle exit plane both of gas-turbine hydrocarbon combustion engine and of ramjet hydrogen combustion engine the relatively large values of concentration of such small components as NO3, HNO2, N2O, HNO3, HNO, NH, N2H, HO2, H2O2 may be realized. The exact definition of these component concentration as well as concentration of NO(x), OH, SO2, O, H, H2, H2O at the nozzle exit plane is very important for plume chemistry. (2) The results which were obtained for subsonic and hypersonic aircrafts indicate on the considerable change of the composition of the gas mixture along the plume. This change can be caused not only by the mixture of combustion products with the atmosphere air but by proceeding of whole complex of nonequilibrium photochemical reactions. The photodissociation processes begin to influence on the formation of the free atoms and radicals at flight altitude H greater than or equal to 18 km. Neglect of these processes can result in essential (up to 10(exp 4) times) mistakes of values gamma(sub OH), gamma(sub O), gamma(sub H), gamma(sub HSO3) and some products of CFC's disintegration. It was found that penetration of Cl-containing species from the atmosphere into the exhaust flow and its interaction with nitrogen oxides leads to essential increasing of the concentration of Cl, Cl2, ClO2, ClNO3, CH3Cl and sometimes HCl and the decreasing of ClO concentration by comparison with background values. The results of our analysis show that the plume aircraft with both hydrocarbon and hydrogen combustion engine may be source of various pollutant components such as HNO, HNO4,ClO2, CH3NO2, CH3NO3, CH2O, Cl, H2O2, but not only NO, NO2, HNO2, HNO3, N2O5, SO2, SO3, H2SO4 as it was supposed before.
Starik, Alexander M.↗