An algorithm for bubble packing method based unstructured grid generation of a curved-edge polygon is developed to avoid bubble departure from a curved boundary during dynamic bubble movement. The curve boundary is ma...
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An algorithm for bubble packing method based unstructured grid generation of a curved-edge polygon is developed to avoid bubble departure from a curved boundary during dynamic bubble movement. The curve boundary is mapped into a straight line to allow bubble adding and moving. Then the bubble position is mapped into the curve boundary by the arc-length parameterization method. Combined with conventional methods, a new method to judge a point in a given curved-edge polygon is proposed. Local grid refinement is realized by adding different size bubbles to the real and artificial vertices and setting the bubble's radius by the weighted average method. Moreover, the SIMPLE algorithm on unstructured collocated grid systems is developed and applied to simulate the lid-driven flow in a polar cavity. The numerical simulation results agree well with the experimental data under different Reynolds numbers.
An experimental study has been performed to investigate pool water instantaneous flash evaporation in a rectangle chamber. The water level was at 40 mm, 60 mm, 100 mm, 150 mm. Initial conditions of the liquid varied f...
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An experimental study has been performed to investigate pool water instantaneous flash evaporation in a rectangle chamber. The water level was at 40 mm, 60 mm, 100 mm, 150 mm. Initial conditions of the liquid varied from 55 to 88C temperature and 3 to 35C superheat. Visualization of the phenomenon using a CCD camera lets us firstly point out the influence of the initial conditions on the flashing phenomenon. The experimental results show that at a constant initial water temperature, the greater the superheat approaches, the more quickly the liquid temperature will decrease. At a constant superheat, the initial water temperature has little influence on the decrease rate of the water temperature. The higher the water level will be, the slower the water temperature will decrease as well as the higher the water temperature will be when the flashing is finished. Experimental study allows us to correlate the water temperature with the initial water temperature and the superheat while flashing is going.
In present paper, the effect of velocity ratio on plane mixing layer is experimentally investigated with Particle Image Velocimetry (PIV). The velocity ratio between low- and high-speed side are 0.25, 0.33 and 0.50, r...
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In present paper, the effect of velocity ratio on plane mixing layer is experimentally investigated with Particle Image Velocimetry (PIV). The velocity ratio between low- and high-speed side are 0.25, 0.33 and 0.50, respectively. The Reynolds number based on the velocity difference of two streams and hydraulic diameter of the channel ranges from 15840~132000. The results indicate that the maximum mean Reynolds stress on the same cross section increases with Reynolds number increasing but decreases with velocity ratio increasing at the equal Reynolds number. The mean vorticity increases with Reynolds number increasing on the same cross-section and increases with the velocity ratio increasing at the equal Reynolds number. The maximum non-dimensional mean vorticity decreases according to an exponential law along the stream-wise direction, and the decreasing speed of maximum mean vorticity increases with the velocity ratio increasing.
Turbulent mixing layer flow was simulated by the discrete vortex method, and viscosity was modeled by the random walk method and the solid wall was represented by the vortex sheet in the simulation. The predictions of...
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Turbulent mixing layer flow was simulated by the discrete vortex method, and viscosity was modeled by the random walk method and the solid wall was represented by the vortex sheet in the simulation. The predictions of the profiles of mean velocity and turbulent flow parameters agree well with experimental data. The results show that the peak value of Reynolds shear stress increases but the fluctuations of the peak value occur because of vortex-pairing, and vorticity peak value increases in the downstream direction. Then the effect of Reynolds number on the distribution of the turbulent flow parameters at the same velocity ratio was explored. It seems that the peak values of Reynolds shear stress under different Reynolds numbers will increase at the similar slope in the downstream direction. The average vorticity peak value will decrease in the downstream direction, and the decrease rate will increase with Reynolds number. In addition, the vorticity peak value in each section will increase nearly linearly with Reynolds number.
In this paper, the characteristics of effervescent atomization are studied experimentally. A high speed camera was used to record the bubbling process and the change of the flow regime in the mixing chamber. Three typ...
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The explosion limits of dimethyl ether, methane and different mixtures of dimethyl ether and methane were measured under the temperature ranging from room temperature to 80C and the pressure ranging from 0.1 to 0.3 MP...
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The explosion limits of dimethyl ether, methane and different mixtures of dimethyl ether and methane were measured under the temperature ranging from room temperature to 80C and the pressure ranging from 0.1 to 0.3 MPa. In addition, the effects of temperature and pressure on the explosion limit were analyzed, and the accuracies of some theoretical calculation models of explosion limit were tested with the experimental results.
High-temperature steam injection is a common means of thermal recovery of thick oil. Although the steam injection boiler currently used for thick oil injection can achieve fast start-stop control, the power consumptio...
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Coal-fired power generation units are characterized by large inertia, strong coupling, and high delay, making dynamic characteristic modeling inherently complex and computationally intensive. To address this, this pap...
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The dimension of erythrocyte is close to capillary diameter and in microcirculation blood should be treated as a two-phase flow system, i.e., erythrocytes suspended in plasma. The rheological property of erythrocytes ...
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The dimension of erythrocyte is close to capillary diameter and in microcirculation blood should be treated as a two-phase flow system, i.e., erythrocytes suspended in plasma. The rheological property of erythrocytes will significantly influence the hemodynamics. In our experiment, the motion and deformation of erythrocytes in a microfluidic chip with rectangular cross-section microchannel was captured by optical microscope and high speed CCD camera. The aggregation, deformation and common movement forms of erythrocytes were observed under different viscosity, hematocrit and velocity. It was found that erythrocytes behaved a regular biconcave disc shape at low velocity and low-to-medium viscosity, and always rolled and rotated themselves in their movement. At high velocity and medium viscosity, RBCs elongated obviously along the flow direction and presented a flat oval shape together with a tank-treading motion (TTM).
Thermoacoustic phenomena are almost nonlinear, which features self-excited onset. In this paper, a closed-open Rijke tube with the heat source placed at the middle of the tube is modeled. Based on parallel computation...
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Thermoacoustic phenomena are almost nonlinear, which features self-excited onset. In this paper, a closed-open Rijke tube with the heat source placed at the middle of the tube is modeled. Based on parallel computation, onset of the Rijke tube is carried out numerically. Onset phenomena with various initial fields are observed. Oscillating frequency of the gas within limit cycle is obtained. The gas flow and heat transfer characteristics are studied. These numerical results agree well with those from previous numerical simulations. Such work is helpful for better understanding on the thermoacoustic phenomena, and offers a reference for the study of the thermoacoustic problems with mesoscopic methods such as the lattice Boltzmann method.
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