APPLICATION OF THE HIGH-RESOLUTION RANS/ILES TECHNOLOGY FOR FLOW SIMULATION AND THE NEARBY ACOUSTIC FIELD OF NEAR-WALL JETS AND MIXING LAYERS

The study of flows with a high degree of turbulence in boundary layers, near-wall jets, gas curtains, separated flows behind various obstacles, as well as during combustion is of great importance for increasing energy efficiency of the flow around various elements in the ducts of gas-dynamic installations. This paper gives some general characteristics of experimental work on the study of friction and heat transfer on a smooth surface, in near-wall jets, and gas curtains under conditions of increased free-stream turbulence. Taking into account the significant effect of high external turbulence on dynamics and heat transfer of separated flows, a similar effect on the flow behind various obstacles is analyzed. First of all, the classical cases of flow separation behind a single backward-facing step and a rib are considered. Then, more complex cases of the flow around a rib oriented at different angles to the flow are analyzed, as well as a system of ribs and a transverse trench with straight and inclined walls in a turbulent flow around them. The features of separated flow in a turbulized stream around a cylinder, leading to an increase in the width of the vortex wake, frequency of vortex separation, and increase in the average heat transfer coefficient are analyzed. The experimental results of the author are compared with data of other researchers. The structure of separated flow at high turbulence—characteristic dimensions of the separation region, parameters of the mixing layer, and pressure distribution—are compared with the conditions of low-turbulent flow. Much attention is paid to thermal characteristics: temperature profiles across the shear layer, temperature distributions over the surface, and local and average heat transfer coefficients. It is shown that external turbulence has a much stronger effect on the separated flow than on the boundary layer on a flat surface. For separated flows, its intensifying effect on heat transfer is more pronounced behind a rib than behind a step. The factor of heat transfer intensification by external turbulence is most pronounced in the transverse cavity and in the system of ribs.

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3-Dimensional modeling of 2014-Malin Landslide, Maharashtra using satellite-derived data: A quantitative approach to numerical simulation technique

10.5194/nhess-2017-382 ◽

2018 ◽

Cited By ~ 1

Author(s):

Shovan Lal Chattoraj ◽

Prashant K. Champati ray ◽

Sudhakar Pardeshi ◽

Vikram Gupta ◽

Yateesh Ketholia

Keyword(s):

High Resolution ◽

Debris Flow ◽

Flow Simulation ◽

Simulation Models ◽

Quantitative Information ◽

Simulation Technique ◽

Maximum Height ◽

Deccan Volcanic Province ◽

South Indian ◽

High Resolution Satellite Images

Abstract. Debris flows, a type of landslides, are not nowadays limited only to the periodic devastation of the geologically fragile Himalaya but also ubiquitous in weathered Deccan Volcanic Province of the cratonic south Indian peninsula. Comprehensive assessment of landslide hazard, pertinently, requires process-based modeling using simulation methods. Development of precipitation triggered debris flow simulation models of real events are still at a young stage in India, albeit, especially in tectonically less disturbed regions. A highly objective simulation technique has therefore been envisaged herein to model the debris flow run-out happened in Malin. This takes cues from a high- resolution DEM and other ancillary ground data including geotechnical and frictional parameters. The algorithm is based on Voellmy frictional (dry and turbulent frictional coefficients, μ and ξ respectively) parameters of debris flow with pre-defined release area identified on high-resolution satellite images like LISS-IV and Cartosat-1. The model provides critical quantitative information on flow 1) Velocity, 2) Height, 3) Momentum, and 4) Pressure along the entrainment path. The simulated velocity of about 16 m/s at mid-way the slide plummeted to 6.2 m/s at the base with intermittently increased and decreased values. The simulated maximum height was 3.9 m which gradually declined to 1.5 m near the bottom. The results can be beneficial in engineering intervention like the construction of check dams to digest the initial thrust of the flow and other remedial measures designed for vulnerable slope protection.

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Near-Wall Modeling of Plane Turbulent Wall Jets

Journal of Fluids Engineering ◽

10.1115/1.2819135 ◽

1997 ◽

Vol 119 (2) ◽

pp. 304-313 ◽

Cited By ~ 28

Author(s):

G. Gerodimos ◽

R. M. C. So

Keyword(s):

Boundary Layer ◽

Outer Region ◽

Plane Wall ◽

Equation Modeling ◽

Wall Jets ◽

Free Jet ◽

Turbulent Wall Jets ◽

Turbulent Wall ◽

Simple Flows ◽

Near Wall

In most two-dimensional simple turbulent flows, the location of zero shear usually coincides with that of vanishing mean velocity gradient. However, such is not the case for plane turbulent wall jets. This could be due to the fact that the driving potential is the jet exit momentum, which gives rise to an outer region that resembles a free jet and an inner layer that is similar to a boundary layer. The interaction of a free-jet like flow with a boundary-layer type flow distinguishes the plane wall jet from other simple flows. Consequently, in the past, two-equation turbulence models are seldom able to predict the jet spread correctly. The present study investigates the appropriateness of two-equation modeling; particularly the importance of near-wall modeling and the validity of the equilibrium turbulence assumption. An improved near-wall model and three others are analyzed and their predictions are compared with recent measurements of plane wall jets. The jet spread is calculated correctly by the improved model, which is able to replicate the mixing behavior between the outer jet-like and inner wall layer and is asymptotically consistent. Good agreement with other measured quantities is also obtained. However, other near-wall models tested are also capable of reproducing the Reynolds-number effects of plane wall jets, but their predictions of the jet spread are incorrect.

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A near-wall strategy for buoyancy-affected turbulent flows using stabilized FEM with applications to indoor air flow simulation

Computer Methods in Applied Mechanics and Engineering ◽

10.1016/j.cma.2004.10.003 ◽

2005 ◽

Vol 194 (36-38) ◽

pp. 3797-3816 ◽

Cited By ~ 8

Author(s):

Tobias Knopp ◽

Gert Lube ◽

Ralf Gritzki ◽

Markus Rösler

Keyword(s):

Turbulent Flows ◽

Indoor Air ◽

Air Flow ◽

Flow Simulation ◽

Indoor Air Flow ◽

Near Wall

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Investigation of Turbulent Wall Jets over Logarithmic Spirai Surfaces : 2nd Report, Properties of Flow near Wall

Transactions of the Japan Society of Mechanical Engineers ◽

10.1299/kikai1938.39.2120 ◽

1973 ◽

Vol 39 (323) ◽

pp. 2120-2128

Author(s):

Kyoji KAMEMOTO

Keyword(s):

Wall Jets ◽

Turbulent Wall Jets ◽

Turbulent Wall ◽

Near Wall

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Investigation of Turbulent Wall Jets over Logarithmic Spiral Surfaces : 2nd Report, Properties of Flow near Wall

Bulletin of JSME ◽

10.1299/jsme1958.17.343 ◽

1974 ◽

Vol 17 (105) ◽

pp. 343-350 ◽

Cited By ~ 1

Author(s):

Kyoji KAMEMOTO

Keyword(s):

Logarithmic Spiral ◽

Wall Jets ◽

Turbulent Wall Jets ◽

Spiral Surfaces ◽

Turbulent Wall ◽

Near Wall

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Delineating wetland catchments and modeling hydrologic connectivity using lidar data and aerial imagery

Hydrology and Earth System Sciences ◽

10.5194/hess-21-3579-2017 ◽

2017 ◽

Vol 21 (7) ◽

pp. 3579-3595 ◽

Cited By ~ 32

Author(s):

Qiusheng Wu ◽

Charles R. Lane

Keyword(s):

High Resolution ◽

Spatial Data ◽

Overland Flow ◽

Flow Simulation ◽

Hierarchical Structures ◽

Aerial Imagery ◽

Lidar Data ◽

Hydrologic Connectivity ◽

Least Cost Path ◽

Elevation Model

Abstract. In traditional watershed delineation and topographic modeling, surface depressions are generally treated as spurious features and simply removed from a digital elevation model (DEM) to enforce flow continuity of water across the topographic surface to the watershed outlets. In reality, however, many depressions in the DEM are actual wetland landscape features with seasonal to permanent inundation patterning characterized by nested hierarchical structures and dynamic filling–spilling–merging surface-water hydrological processes. Differentiating and appropriately processing such ecohydrologically meaningful features remains a major technical terrain-processing challenge, particularly as high-resolution spatial data are increasingly used to support modeling and geographic analysis needs. The objectives of this study were to delineate hierarchical wetland catchments and model their hydrologic connectivity using high-resolution lidar data and aerial imagery. The graph-theory-based contour tree method was used to delineate the hierarchical wetland catchments and characterize their geometric and topological properties. Potential hydrologic connectivity between wetlands and streams were simulated using the least-cost-path algorithm. The resulting flow network delineated potential flow paths connecting wetland depressions to each other or to the river network on scales finer than those available through the National Hydrography Dataset. The results demonstrated that our proposed framework is promising for improving overland flow simulation and hydrologic connectivity analysis.

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