China
Africa
Explore chapters and articles related to this topic
A New Approach for Parkinson's Disease Imaging Diagnosis Using Digitized Spiral Drawing
Published in Ashish Mishra, G. Suseendran, Trung-Nghia Phung, Soft Computing Applications and Techniques in Healthcare, 2020
The two features introduced are as follows: Radial velocity: The radial velocity of an object with respect to a given point is the rate of change of the distance between the object and the point. A spiral drawn by a patient or healthy control is analysed for this feature with reference to origin. Radial velocity is calculated by dividing distance between two consecutive points (displacement) by signed angle between the ray ending at the origin and passing through the point (x, y) on spiral. Python numpy library function atan2 method returns a numeric value in radians representing the angle between the ray passing through (x, y) and positive x axis.Normalised radial velocity: Radial velocity with time is the change of radial velocity between any two consecutive points on spiral over the time elapsed.
Inviscid Flow
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
Source flow can be described as a radially outward flow emanating from a point. The velocity in the xy plane is radial at any location, as is illustrated in Figure 12.10. At any location along a circle of radius r, the radial velocity Vr is a constant. The flow rate per unit length into the page is a constant that is equal to the product of radial velocity and circumferential distance: QL=q=2πrVr
Effects of the impeller blade geometry on the performance of a turbo pneumatic separator
Published in Chemical Engineering Communications, 2018
Haipeng Zhao, Jiaxiang Liu, Yuan Yu
The comparison of radial velocity contours in the channel of the S-RB, N-RB, and P-RB impellers is described in Figure 6. The velocity values can be observed in the colorimetric column and the negative sign indicates that the radial velocity points towards the center of impeller. For the S-RB type, the velocity gradient is from −5 m/s to 0.5 m/s. The velocity gradient of the N-RB type is from −5.5 m/s to 1 m/s and the velocity gradient of the P-RB type is from −3.5 m/s to −2.5 m/s. Obviously, the velocity gradient of the S-RB type and N-RB type are larger than that of the P-RB type. A large velocity gradient will cause the instability of particle movement (Liu et al, 2015). Moreover, the air vortex is generated near the suction side of S-RB and N-RB types so that some of the fine particles that are dragged into the channel on impeller will probably be returned to the annular region and mixed with as the coarse particles by the positive radial velocity (0.5 m/s or 1 m/s), leading to fish-hook effect and decreasing the classification accuracy. However, for the P-RB type, there is no air vortex caused in the channel of impeller, reducing the possibilities of the fine particles back-mixing and improving the classification performance.
Direct numerical simulation of transitional flow in a finite length curved pipe
Published in Journal of Turbulence, 2018
Amirreza Hashemi, Paul F. Fischer, Francis Loth
Poiseuille flow enters the straight pipe and remains nearly parabolic at the start of the pipe curvature and begins to skew towards the outer wall over the first quarter of the curved section for both Reynolds number 5200 and 6200. Low- and high-pressure regions are present near the inner and outer walls, respectively, as expected for Dean’s flow. The small axial velocity (low kinetic energy) near the inner wall after the first quarter of the curved pipe coupled with the low-pressure region provides a potentially unstable region. Velocity in this region becomes complicated and potentially unstable both for Re = 5200 and 6200. Radial velocity is shown to change sign in a short space indicating larger velocity gradients. As the flow goes along the curved pipe, flow near inner wall accelerates, the unstable region moves towards the centre, and the velocity profile appears divided. In the second half of the curved pipe, there exists an interaction between two jets on inner and outer walls near the~centre. Figures 10 and 11 show the velocity vector plot in different cross sections along the curved pipe for the same Reynolds numbers. The cross sections are in the first half of the curved pipe for every π/16 radians also at a location three diameters upstream to start of pipe curvature which show the evolution of secondary flow.
Verification and validation of a variable–density solver for fire safety applications
Published in Numerical Heat Transfer, Part B: Fundamentals, 2019
L. Ma, F. Nmira, J. L. Consalvi
The algorithm was applied to the LES of large-scale buoyant helium plumes. From these simulations, the following conclusions can be drawn: Predictions with DSM and DEDM capture the plume dynamics but underestimate the mixing rate at vicinity of the plume centerline.Puffing frequency, mean axial velocity, and mean and fluctuations of radial velocity are insensitive to grid refinements and SGS scalar flux models. This result is of significant importance for fire modeling since radial velocity controls the air entrainment. In opposite way, fluctuations of axial velocity and mean and fluctuations of helium concentration are affected by both mesh refinement and SGS scalar flux models.The DGGM and DLGGM provide similar results and improve mixing rate predictions as compared to the DEDM, especially for m. Adding gradient model with the DEDM improves the DEDM whereas combining it to the DGGM has no noticeable effects on the predictions of the DGGM.Grid refinement improves more significantly helium mass fraction and its fluctuation than SGS scalar closures. This suggests that the small-scale buoyancy effects are not fully captured by the present LES.Model predictions are comparable with those provided by state-of-the-art codes devoted to fire simulations and can be used for future investigations on fire safety applications.