scholarly journals FLOW IN A TWO-DIMENSIONAL SQUARE CAVITY : A COMPARISON BETWEEN FLOW VISUALIZATION EXPERIMENT AND NUMERICAL CALCULATIONS

1986 ◽  
Vol 29 (258) ◽  
pp. 4103-4106 ◽  
Author(s):  
Osamu MOCHIZUKI ◽  
Haruo YAMABE ◽  
Hideo YAMADA
Keyword(s):  
Flow Visualization ◽  
Numerical Calculations ◽  
Two Dimensional ◽  
Square Cavity ◽  
Visualization Experiment

Numerical analysis and explore of asymmetrical fluid flow in a two-sided lid-driven cavity

2020 ◽  
Vol 14 (3) ◽  
pp. 7269-7281
Author(s):  
El Amin Azzouz ◽  
Samir Houat
Keyword(s):  
Velocity Ratio ◽  
Two Dimensional ◽  
Lower Side ◽  
Square Cavity ◽  
Driven Cavity ◽  
Parallel Motion ◽  
Bottom Cavity ◽  
Secondary Vortices ◽  
Volume Method ◽  
Fluid Characteristics

The two-dimensional asymmetrical flow in a two-sided lid-driven square cavity is numerically analyzed by the finite volume method (FVM). The top and bottom walls slide in parallel and antiparallel motions with various velocity ratio (UT/Ub=λ) where |λ|=2, 4, 8, and 10. In this study, the Reynolds number Re1 = 200, 400, 800 and 1000 is applied for the upper side and Re2 = 100 constant on the lower side. The numerical results are presented in terms of streamlines, vorticity contours and velocity profiles. These results reveal the effect of varying the velocity ratio and consequently the Reynolds ratio on the flow behaviour and fluid characteristics inside the cavity. Unlike conventional symmetrical driven flows, asymmetrical flow patterns and velocity distributions distinct the bulk of the cavity with the rising Reynolds ratio. For λ>2, in addition to the main vortex, the parallel motion of the walls induces two secondary vortices near the bottom cavity corners. however, the antiparallel motion generates two secondary vortices on the bottom right corner. The parallel flow proves affected considerably compared to the antiparallel flow.

PHOTOLUMINESCENCE OF IMPURITY-BOUND EXCITONS AND TRIONS IN MAGNETIC FIELDS

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1558-1562
Author(s):  
ARKADIUSZ WÓJS ◽  
LESZEK BRYJA ◽  
ANNA GŁADYSIEWICZ ◽  
JAN MISIEWICZ ◽  
MAREK POTEMSKI
Keyword(s):  
Magnetic Fields ◽  
Low Energy ◽  
Numerical Calculations ◽  
Two Dimensional ◽  
Recombination Spectrum

Recombination spectrum of excitons and positive trions is studied by two-beam magneto-photoluminescence of a two-dimensional hole gas. For acceptor-bound trions a low-energy cyclotron replica is observed, corresponding to a hole shake-up process. The experiment is supplemented by realistic numerical calculations, allowing for identification of individual transitions and connecting the splitting of the shake-up line directly with the hole mass.

scholarly journals Direct Observation of Filling Process and Porosity Prediction in High Pressure Die Casting

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1099 ◽  
Author(s):  
Hanxue Cao ◽  
Chao Shen ◽  
Chengcheng Wang ◽  
Hui Xu ◽  
Juanjuan Zhu
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Flow Visualization ◽  
Flow Pattern ◽  
Experimental Verification ◽  
Die Casting ◽  
Filling Process ◽  
High Pressure Die Casting ◽  
Visualization Experiment ◽  
Pressure Die Casting

Although numerical simulation accuracy makes progress rapidly, it is in an insufficient phase because of complicated phenomena of the filling process and difficulty of experimental verification in high pressure die casting (HPDC), especially in thin-wall complex die-castings. Therefore, in this paper, a flow visualization experiment is conducted, and the porosity at different locations is predicted under three different fast shot velocities. The differences in flow pattern between the actual filling process and the numerical simulation are compared. It shows that the flow visualization experiment can directly observe the actual and real-time filling process and could be an effective experimental verification method for the accuracy of the flow simulation model in HPDC. Moreover, significant differences start to appear in the flow pattern between the actual experiment and the Anycasting solution after the fragment or atomization formation. Finally, the fast shot velocity would determine the position at which the back flow meets the incoming flow. The junction of two streams of fluid would create more porosity than the other location. There is a transition in flow patterns due to drag crisis under high fast shot velocity around two staggered cylinders, which resulted in the porosity relationship also changing from R1 < R3 < R2 (0.88 m/s) to R1 < R2 < R3 (1.59 and 2.34 m/s).

Experimental and Numerical Investigation on Film Cooling Performance and Flow Structure of Film Holes

2019 ◽  
Author(s):  
Nan Cao ◽  
Xue Li ◽  
Ze-yu Wu ◽  
Xiang Luo
Keyword(s):  
Flow Visualization ◽  
Numerical Investigation ◽  
Flow Structure ◽  
Film Cooling ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Visualization Experiment ◽  
Shaped Hole

Abstract Discrete hole film cooling has been commonly used as an effective cooling technique to protect gas turbine blades from hot gas. There have been numerous investigations on the cylindrical hole and shaped hole, but few experimental investigations on the cooling mechanism of the novel film holes with side holes (anti-vortex hole and sister hole) are available. This paper presents an experimental and numerical investigation to study the film cooling performance and flow structure of four kinds of film holes (cylindrical hole, fan-shaped hole, anti-vortex hole and sister hole) on the flat plate. The film holes have the same main hole diameter of 4mm and the same inclination angle of 45°. The adiabatic film cooling effectiveness is obtained by the steady-state Thermochromic Liquid Crystal (TLC). The flow visualization experiment and numerical investigation are performed to investigate the flow structure and counter-rotating vortex pair (CRVP) intensity. The smoke is selected as the tracer particle in the flow visualization experiment. The mainstream Reynolds number is 2900, the blowing ratio ranges from 0.3 to 2.0, and the density ratio of coolant to mainstream is 1.065. Experimental results show that compared with the cylindrical hole, the film cooling performance of the anti-vortex hole and sister hole shows significant improvement at all blowing ratios. The sister hole can achieve the best cooling performance at blowing ratios of 0.3 to 1.5. The fan-shaped hole only performs well at high blowing ratios and it performs best at the blowing ratio of 2.0. Flow visualization experiment and numerical investigation reveal that the anti-vortex hole and sister hole can decrease the CRVP intensity of the main hole and suppress the coolant lift-off because of side holes, which increases the film coverage and cooling effectiveness. For the sister hole, the side holes are parallel to the main hole, but for the anti-vortex hole, there are lateral angles between them. The coolant interaction between the side holes and main hole of the sister hole is stronger than that of the anti-vortex hole. Therefore, the sister hole provides better film cooling performance than the anti-vortex hole.

First-passage time for a particular stationary periodic Gaussian process

1976 ◽  
Vol 13 (01) ◽  
pp. 27-38 ◽  
Author(s):  
L. A. Shepp ◽  
D. Slepian
Keyword(s):  
Gaussian Process ◽  
Infinite Series ◽  
First Passage Time ◽  
Passage Time ◽  
Numerical Calculations ◽  
Time Interval ◽  
Two Dimensional ◽  
First Passage ◽  
Gaussian Density ◽  
First Passage Probability

We find the first-passage probability that X(t) remains above a level a throughout a time interval of length T given X(0) = x 0 for the particular stationary Gaussian process X with mean zero and (sawtooth) covariance P(τ) = 1 – α | τ |, | τ | ≦ 1, with ρ(τ + 2) = ρ(τ), – ∞ &lt; τ &lt; ∞. The desired probability is explicitly found as an infinite series of integrals of a two-dimensional Gaussian density over sectors. Simpler expressions are found for the case a = 0 and also for the unconditioned probability that X(t) be non-negative throughout [0, T]. Results of some numerical calculations are given.

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