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The interaction of a turbulent, spatially developing crossflow with a transverse jet possesses several engineering and technological applications such as film cooling of turbine blades, exhaust plumes, thrust vector control, fuel injection, etc. Direct Numerical Simulation (DNS) of a jet in a crossflow under different streamwise pressure gradients (zero and favorable pressure gradient) is carried out. The purpose is to study the physics behind the transport phenomena and coherent structure dynamics in turbulent crossflow jets at different streamwise pressure gradients and low/high-velocity ratios (0.5 and 1). The temperature was regarded as a passive scalar with a molecular Prandtl number of 0.71. The analysis is performed by prescribing accurate turbulent information (instantaneous velocity and temperature) at the inlet of a computational domain. The upward motion of low-momentum fluid created by the “legs” of the counter-rotating vortex pair (CVP) encounters the downward inviscid flow coming from outside of the turbulent boundary layer, inducing a stagnation point and a shear layer. This layer is characterized by high levels of turbulent mixing, turbulence production, turbulent kinetic energy (TKE) and thermal fluctuations. The formation and development of the above-mentioned shear layer are more evident at higher velocity ratios.
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Liquid Coolant Jet Breakup with Application to Grinding
Liquid jets in surrounding air face capillary and shear forces which eventually disintegrate the jet into droplets or spray. The instabilities developed in the flow inevitably break down an initial laminar (coherent) jet into a turbulent one. In the manufacturing process called grinding, one of the oldest approaches of shaping metals and other materials, liquid coolant jets are frequently used. A non-coherent or turbulent jet has a reduced flow rate due to cavitation, air entrapment and atomization of the fluid particles. The jet spread does not allow the coolant jet to effectively breach the high-speed rotating air layer, created by entrainment of air along the surface of rapidly rotating grinding wheel. The coherent, nearly columnal jet should be sufficiently long to maintain its initial velocity to penetrate the layer of air rotating with the grinding wheel. Thus, in many critical grinding applications, it is advised to use a coherent jet instead of a spray to eradicate defects of ground surface. In this study, we present simulations of liquid jet flows to see how the jet develops and breaks due to surface tension and shear forces. Creating an accurate model to predict liquid jet characteristics, especially for high-speed applications such as grinding wheel cooling would require wellresolving numerical grids and turbulence model selection. The problem being multi-phased with a density ratio of coolant-to-air being order of 1000 adds to the computational complexity. The presented numerical model and results are different compared to the previous simulations of liquid jets as the characteristics of jet disintegration are explored under conditions that closely resemble a grinding cooling application. Finite volume discretization of the flow domain and calculation of flow field characteristics were done by commercial software ANSYS Mesh and ANSYS Fluent modules, respectively. The numerical calculation and visualization of disintegration of free jet and the jet impinging into grinding wheel will be presented.
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- Award ID(s):
- 2333138
- PAR ID:
- 10613843
- Publisher / Repository:
- American Institute of Aeronautics and Astronautics
- Date Published:
- ISBN:
- 978-1-62410-730-6
- Format(s):
- Medium: X
- Location:
- Multiple Locations
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2024-85879
