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Oct 31, 2024 | 
pubs.aip.org | R. Pramanik |A-Man Zhang |Yinxiang Ma
When a shock wave crosses a density interface, the Richtmyer–Meshkov instability causes perturbations to grow. Richtmyer–Meshkov instabilities arise from the deposition of vorticity from the misaligned density and pressure gradients at the shock front. In many engineering applications, microscopic surface roughness will grow into multi-mode perturbations, inducing mixing between the fluid on either side of an initial interface.
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Oct 30, 2024 | 
pubs.aip.org | R. Pramanik |A-Man Zhang |Yinxiang Ma
Oil-in-water (O/W) emulsions are widely used in industrial production, food science, petrochemicals, and other fields. Quantitative measurement of the interaction between droplets is essential for the in-depth understanding of the stability mechanism of O/W emulsions. Optical tweezers are able to accurately and quantitatively measure the interaction forces between droplets in oil-in-water emulsion systems at the microscopic scale and offer numerous advantages.
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Oct 28, 2024 | 
pubs.aip.org | Shanghai Jiao Tong |Yinxiang Ma |A-Man Zhang |R. Pramanik
Acceleration of objects in fluids widely exists in biological propulsions and contains rich unsteady fluid mechanisms. In this paper, the instantaneous drag force on accelerating normal flat plates (circular, elliptical, square, and rectangular plates) in a wide range of dimensionless acceleration ( ) is measured, and the underlying mechanism for force generation is investigated.
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Oct 25, 2024 | 
pubs.aip.org | Aerospace Engineering |Yinxiang Ma |A-Man Zhang |R. Pramanik
This experimental study investigates the fluid dynamic function of butterfly scales to reduce friction drag below that experienced in a laminar boundary layer. A previous study on flight-testing live monarch butterflies showed that the removal of the scales from the wings had a significant effect on reducing flying efficiency.
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Oct 18, 2024 | 
pubs.aip.org | Yinxiang Ma |Zengshun Chen |A-Man Zhang |S. J. Kim
In a theoretical point of view, a stagnation flow is characterized by its viscous flow-like behavior due to its very low inertial contribution.53,54 The flow stagnation can be quantified by comparing the inertial term, ρa(u·∇u), and the viscous term, μa∇2u, in the Navier–Stokes equation, yielding the inertial-viscous ratio as where ρa is the air density, u is the flow velocity, and μa is the air viscosity.
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Oct 15, 2024 | 
pubs.aip.org | Yinxiang Ma |Zengshun Chen |A-Man Zhang
The wave dynamics play a crucial role in the operation characteristics of the rotating detonation engine. We conducted numerical simulations of a rotating detonation combustor (RDC) using multicomponent reactive Navier–Stokes equations coupled with a discrete phases model. The RDC in this research employs a configuration with multiple coaxial injectors supplying oxygen-enriched air and kerosene spray at room temperature.
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Oct 11, 2024 | 
pubs.aip.org | Yinxiang Ma |Crystal Owens |A-Man Zhang
Topics Liquid metals, Computational models, Hydrogen, Pyrolysis, Computational fluid dynamics, Bubble dynamics CCS Carbon capture and storage CFD Computational fluid dynamics LES PBM PCI Pulverized coal injection SMR Subscripts Dimensionless Variables Symbols dni dno HL Initial height of molten media in the column Nmesh Total number of mesh elements QG Volumetric gas injection rate ts Time an observation is started uB uG,n Gas flow velocity at the nozzle exit z Distance from the nozzle exit...
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Oct 9, 2024 | 
pubs.aip.org | Yinxiang Ma |Crystal Owens |A-Man Zhang
In order to further understand the impact of tip air injection on compressor stability under circumferential pressure distortion, a series of experimental studies on tip air injection under uniform and circumferential distortion were conducted on a low-speed single rotor axial flow compressor. The unsteady measurements were carried out by use of microsensors and strain gauges bonded on the rotor blade surfaces, and a collection of dynamic pressure sensors installed on the casing wall.
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Oct 7, 2024 | 
pubs.aip.org | Yinxiang Ma |Crystal Owens |Zengshun Chen
The continuum level hydrodynamic equations of a simple fluid were derived by Irving and Kirkwood directly from discrete particle dynamics using statistical mechanics almost 75 years ago. Their elegant derivation demonstrated the fundamental molecular basis of macroscopic fluid flow and culminated in molecular expressions for the stress tensor and heat current density that have since been employed in countless molecular simulations to date.
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Oct 4, 2024 | 
pubs.aip.org | Swiss Federal Laboratories |Yinxiang Ma
Efficient and accurate analysis of fluid flows is essential in many engineering applications. Such flows are often turbulent since they occur at high Reynolds numbers and involve many length and time scales. The largest scale is often linked to the size of the flow problem. It can, therefore, be the size of a planet in meteorological applications or the length of an aircraft. These large scales then feed energy into smaller scales until they finally dissipate at the very smallest scales.
