Inflow-outflow boundary conditions for two-dimensional acoustic waves in channels with flow
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Watson, Willie R.↗
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Application of a two-layer near wall model to fully developed and rotating channel turbulent flows
The two-layer near wall approach in combination with the k-epsilon model was applied to rotating flows. Validation studies show that the conventional length scales have to be modified to account for rotating effects. Guided by the Lam and Bremhorst's low Reynolds number model with the rotation-corrected k-epsilon model, a new set of length scales formulation is proposed. The developments and validations of the current model are reported. A fully elliptic numerical method developed to solve the two-dimensional Reynolds-averaged Navier-Stokes equations is employed for the computational study.
Chen, C. P.↗
Experiments on Turbulent Flow Through Channels Having Porous Rough Surfaces with or Without Air Injection
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Eckert, E R G↗
West-Antarctic Ice Streams: Analog to Ice Flow in Channels on Mars
Sounding of the sea floor in front of the Ross Ice Shelf in Antarctica recently revealed large persistent patterns of longitudinal megaflutes and drumlinoid forms, which are interpreted to have formed at the base of ice streams during the list glacial advance. The flutes bear remarkable resemblance to longitudinal grooves and highly elongated streamlined islands found on the floors of some large martian channels, called outflow channels. ln addition, other similarities exist between Antarctic ice streams and outflow channels. Ice streams are 30 to 80 km wide and hundreds of kilometers long, as are the martian channels. Ice stream beds are below sea level. Floors of many martian outflow channels lie below martian datum, which may have been close to or below past martian sea levels. The Antarctic ice stream bed gradient is flat and locally may go uphill, and surface slopes are exceptionally low. So are gradients of martian channels. The depth to the bed in ice streams is 1 to 1.5 km. At bankful stage, the depth of the fluid in outflow channels would have been 1 to 2 km. These similarities suggest that the martian outflow channels, whose origin is commonly attributed to gigantic catastrophic floods, were locally filled by ice that left a conspicuous morphologic imprint. Unlike the West-Antarctic-ice streams, which discharge ice from an ice sheet, ice in the martian channels came from water erupting from the ground. In the cold martian environment, this water, if of moderate volume, would eventually freeze. Thus it may have formed icings on springs, ice dams and jams on constrictions in the channel path, or frozen pools. Given sufficient thickness and downhill surface gradient, these ice masses would have moved; and given the right conditions, they could have moved like Antarctic ice streams.
Lucchitta, B. K.↗
Channelized Lava Flows with Density Changes During Emplacement
We explore the effects on emplacement of large basaltic lava flows due to (1) changes in viscosity, (2) formation of channels/levees, and (3) loss of volatiles that cause a change in lava density. These may explain why flows on Mars are not as thick as expected. Additional information is contained in the original extended abstract.
Baloga, S. M.↗
Interference Drag Associated with Engine Locations for Multidisciplinary Design Optimization
This research aims to quantify the interference drag for various engine locations on a traditional “tube and wing,” 150-passenger commercial aircraft flying at 35,000 ft and Mach 0.8. Engine locations are varied in the chord wise, span wise, and vertical directions near the wing, both under and above the wing, as well as along the fuselage. Euler simulations are performed with representative powered modern engines. The results are intended to supplement empirical drag estimates suitable for multidisciplinary design environments. Large interference drag increases, as compared to the isolated air frame and engine geometry, are found to occur when the engine is placed directly above or below the wing. Interference effects are significantly reduced, and in some instances result in benefits compared to the isolated bodies, when the engines are placed fore or aft of the wing. Interference drag increases are partially explained by flow channels leading to choked flow and shock interactions between bodies.
Blaesser, Nathaniel J.↗
Solutions for Subtidal Flow in Channels and Estuaries under Different Integral Constraints
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Michael M. Whitney↗
On the large-eddy simulation of transitional wall-bounded flows
The structure of the subgrid scale fields in plane channel flow has been studied at various stages of the transition process to turbulence. The residual stress and subgrid scale dissipation calculated using velocity fields generated by direct numerical simulations of the Navier-Stokes equations are significantly different from their counterparts in turbulent flows. The subgrid scale dissipation changes sign over extended areas of the channel, indicating energy flow from the small scales to the large scales. This reversed energy cascade becomes less pronounced at the later stages of transition. Standard residual stress models of the Smagorinsky type are excessively dissipative. Rescaling the model constant improves the prediction of the total (integrated) subgrid scale dissipation, but not that of the local one. Despite the somewhat excessive dissipation of the rescaled Smagorinsky model, the results of a large eddy simulation of transition on a flat-plate boundary layer compare quite well with those of a direct simulation, and require only a small fraction of the computational effort. The inclusion of non-dissipative models, which could lead to further improvements, is proposed.
Piomelli, Ugo↗
On the large-eddy simulation of transitional wall-bounded flows
The structure of the subgrid scale fields in plane channel flow has been studied at various stages of the transition process to turbulence. The residual stress and subgrid scale dissipation calculated using velocity fields generated by direct numerical simulations of the Navier-Stokes equations are significantly different from their counterparts in turbulent flows. The subgrid scale dissipation changes sign over extended areas of the channel, indicating energy flow from the small scales to the large scales. This reversed energy cascade becomes less pronounced at the later stages of transition. Standard residual stress models of the Smagorinsky type are excessively dissipative. Rescaling the model constant improves the prediction of the total (integrated) subgrid scale dissipation, but not that of the local one. Despite the somewhat excessive dissipation of the rescaled Smagorinsky model, the results of a large eddy simulation of transition on a flat-plate boundary layer compare quite well with those of a direct simulation, and require only a small fraction of the computational effort. The inclusion of non-dissipative models, which could lead to further improvements, is proposed.
Piomelli, Ugo↗
Finite analytic numerical solution of heat transfer and flow past a square channel cavity
A numerical solution of flow and heat transfer characteristics is obtained by the finite analytic method for a two dimensional laminar channel flow over a two-dimensional square cavity. The finite analytic method utilizes the local analytic solution in a small element of the problem region to form the algebraic equation relating an interior nodal value with its surrounding nodal values. Stable and rapidly converged solutions were obtained for Reynolds numbers ranging to 1000 and Prandtl number to 10. Streamfunction, vorticity and temperature profiles are solved. Local and mean Nusselt number are given. It is found that the separation streamlines between the cavity and channel flow are concave into the cavity at low Reynolds number and convex at high Reynolds number (Re greater than 100) and for square cavity the mean Nusselt number may be approximately correlated with Peclet number as Nu(m) = 0.365 Pe exp 0.2.
Chen, C.-J.↗
Potential Mars Surveyor 2001 Landing Sites Near Apollinaris Patera
Landing sites near Apollinaris Patera are proposed for the Mars Surveyor 2001 lander/rover mission. Regions near the base of Apollinaris Patera provide a unique opportunity within the proposed -15(beta)o 30(beta) latitude belt to sample outcrop lithologies ranging from highland Noachian basement rocks, to Hesperian aged lava flows, channel and flood plain materials, to Amazonian volcanic, ash flow, and channel deposits. Pristine impact craters exhibiting lobate ejecta blankets are found both on the volcano itself and on the surrounding terrain implying a ground water rich environment well into the Amazonian. Therefore its formation likely induced long-lived volcanic-hydrothermal systems, a high priority target for the mission.
Gulick, Virginia C.↗
Potential Mars Surveyor 2001 Landing Sites Near Apollinaris Patera
Landing sites near Apollinaris Patera are proposed for the Mars Surveyor 2001 lander/rover mission. Regions near the base of Apollinaris Patera provide a unique opportunity within the proposed -15 deg to 30deg latitude belt to sample outcrop lithologies ranging from highland Noachian basement rocks, to Hesperian aged lava flows, channel and flood plain materials, to Amazonian volcanic, ash flow, and channel deposits. Pristine impact craters exhibiting lobate ejecta blankets are found both on the volcano itself and on the surrounding terrain implying a ground water rich environment well into the Amazonian. Therefore its formation likely induced long-lived volcanic-hydrothermal systems, a high priority target for the mission.
Gulick, Virginia C.↗
ON THE EMPIRICAL CORRELATION OF CRITICAL BOILING HEAT FLUX FOR CHANNELS OF VARIOUS CROSS SECTIONS AND ORIENTATION
Boiling heat flux in channel flow - criticality factor
CHANNEL FLOW↗
Thermal Modeling of Permafrost Melt by Overlying Lava Flows with Applications to Flow-associated Outflow Channel Volumes in the Cerberus Plains, Mars
The Cerberus region of Mars has numerous geologically recent fluvial and volcanic features superimposed spatially, with some of them using the same flow channels and apparent vent structures. Lava-water interaction landforms such as psuedocraters suggest some interaction of emplacing lava flows with underlying ground ice or water. This study investigates a related interaction type a region where the emplaced lava might have melted underlying ice in the regolith, as there are small outflow channel networks emerging from the flank flows of a lava shield over a portion of the Eastern Cerberus Rupes. Specifically, we use high-resolution Mars Orbiter Laser Altimeter (MOLA) topography to constrain channel and flow dimensions, and thus estimate the thermal pulse from the emplaced lava into the substrate and the resulting melting durations and refreezing intervals. These preliminary thermal models indicate that the observed flows could easily create thermal pulse(s) sufficient to melt enough ground ice to fill the observed fluvial small outflow channels. Depending on flow eruption timing and hydraulic recharge times, this system could easily have produced multiple thermal pulses and fluvial releases. This specific case suggests that regional small water releases from similar cases may be more common than suspected, and that there is a possibility for future fluvial releases if ground ices are currently present and future volcanic eruptions in this young region are possible.
Chase, Z. A. J.↗
FORTRAN program for generating a two-dimensional orthogonal mesh between two arbitrary boundaries
A FORTRAN 4 program is presented which computes and plots coordinates for a two-dimensional orthogonal mesh in the region between the walls of a flow channel. The program is designed for a channel containing a body about which flow passes and which spans the channel from one wall to the other. However, the condition that the channel contain an immersed body can be easily removed from the program. Input to the program consists of spline points of the channel walls and the body geometry. Output includes printed and plotted coordinates of the generated orthogonal mesh and angles of the mesh with the horizontal plane.
Mcnally, W. D.↗
Spiraled channels improve heat transfer between fluids
Spiral flow channels increase heat transfer between two fluids in a countercurrent heat exchanger of given volume. The heat exchanger is constructed by connecting a spiraled bellows-shaped ducting between two concentric cylindrical tubes.
Higa, W.↗
Aerodynamic analysis of the loft anomaly observed on orbital flight tests of the space shuttle
The loft anomaly observed during the launch phase of the orbital flight tests (OFT) of the Space Shuttle is described and evidence that the loft anomaly resulted from previously unobserved aerodynamic phenomena is presented. The anomaly was that the altitude at staging was higher than anticipated. The anticipated altitude profile was predicted on wind tunnel test results that did not accurately simulate the flow between the orbiter vehicle and external tank and did not adequately simulate the engine plumes and thus the base pressures. An analogy is used to relate the flow between the orbiter and external tank to the flow in a two dimensional channel. Plume simulation is identified as a major goal during wind tunnel testing, and a wind tunnel test that was conducted to provide the best possible representation of the plume effect on the channel flow field is described.
Surber, T. E.↗
Relative ages of lava flows at Alba Patera, Mars
Many large lava flows on the flanks of Alba Patera are astonishing in their volume and length. As a suite, these flows suggest tremendously voluminous and sustained eruptions, and provide dimensional boundary conditions typically a factor of 100 larger than terrestrial flows. One of the most striking features associated with Alba Patera is the large, radially oriented lava flows that exhibit a variety of flow morphologies. These include sheet flows, tube fed and tube channel flows, and undifferentiated flows. Three groups of flows were studied; flows on the northwest flank, southeast flank, and the intracaldera region. The lava flows discussed probably were erupted as a group during the same major volcanic episode as suggested by the data presented. Absolute ages are poorly constrained for both the individual flows and shield, due in part to disagreement as to which absolute age curve is representative for Mars. A relative age sequence is implied but lacks precision due to the closeness of the size frequency curves.
Schneeberger, Dale M.↗