Developing Region of Laminar Jets With Parabolic Exit Velocity Profiles

1981 ◽  
Vol 103 (2) ◽  
pp. 322-327 ◽  
Author(s):  
G. W. Rankin ◽  
K. Sridhar
Keyword(s):  
Experimental Data ◽  
Approximate Solution ◽  
Velocity Distribution ◽  
Velocity Profiles ◽  
Exit Velocity ◽  
Parabolic Profile ◽  
Laminar Jet ◽  
Laminar Jets ◽  
Developing Region

An approximate solution to the velocity distribution in a submerged axisymmetric, laminar jet which issues from a long tube is presented. The solution is a modification of that of Okabe [17] and takes into account the changes that occur in the parabolic profile downstream of the jet exit. Comparisons are made with experimental data and other approximate theories taken from the literature.

Turn-ON and Turn-OFF Times for a Laminar Jet

1973 ◽  
Vol 95 (2) ◽  
pp. 155-160 ◽  
Author(s):  
S. Abramovich ◽  
A. Solan
Keyword(s):  
Experimental Data ◽  
Time Lag ◽  
Experimental Results ◽  
Time Lags ◽  
Laminar Jet ◽  
Turn On ◽  
Switching Times ◽  
Laminar Jets ◽  
Jet Nozzle ◽  
Time Required

Experimental results of the speed of travel of a disturbance in front of suddenly switched-on and switched-off submerged laminar jets are presented. The results show that the time lag for a switched-off jet is approximately one half the time required for a particle moving in front of a switched on jet to reach a certain distance from the jet nozzle. The time lags for an instantaneous change in the jet intensity is approximately the same as that for switching the whole jet on and off. These experimental data can be used to calculate the switching times of turbulence amplifiers.

Developing Region of Laminar Jets With Uniform Exit Velocity Profiles

1978 ◽  
Vol 100 (1) ◽  
pp. 55-59 ◽  
Author(s):  
G. W. Rankin ◽  
K. Sridhar
Keyword(s):  
Shear Layer ◽  
Graphical Method ◽  
Integral Form ◽  
Free Shear Layer ◽  
Potential Core ◽  
Laminar Jet ◽  
Laminar Jets ◽  
Present Solution ◽  
Developing Region ◽  
Energy Equations

The integral form of the momentum and energy equations, subject to the boundary layer simplifications, are used to obtain an approximate solution for an axisymmetric laminar jet with a uniform profile at the nozzle exit. The solution is expressed in a closed form. The jet flow field is divided into a developing and developed region. In the developing region a potential core is assumed to exist, bounded by an annular free shear layer, Schlichting’s velocity profile for an axisymmetric laminar jet is assumed in the free shear layer. The present solution is compared with existing experimental and analytical results in the developing region. Also a graphical method for determining the potential core radius and the parameters of the assumed Schlichting profile is given.

Thermal Analysis of the Hot Dip-Coating Process

1993 ◽  
Vol 115 (2) ◽  
pp. 453-460 ◽  
Author(s):  
Hui Zhang ◽  
M. Karim Moallemi ◽  
Sunil Kumar
Keyword(s):  
Experimental Data ◽  
Thermal Analysis ◽  
Approximate Solution ◽  
Dip Coating ◽  
Solution Procedure ◽  
Heat Diffusion ◽  
Coating Process ◽  
Parametric Effects ◽  
Simplifying Assumptions ◽  
Axial Heat

In this study a thermal analysis is performed on the hot dip-coating process where solidification of metal occurs on a bar moving through a finite molten bath. A continuum model is considered that accounts for important transport mechanisms such as axial heat diffusion, buoyancy, and shear-induced melt motion in the bath. A numerical solution procedure is developed, and its predictions are compared with those of an analytical approximate solution, as well as available experimental data. The predictions of the numerical scheme are in good agreement with the experimental data. The results of the approximate solution, however, exhibit significant disagreement with the data, which is attributed to the simplifying assumptions used in its development. Parametric effects of the bath geometry, and initial and boundary temperatures and solid velocity, as characterized by the Reynolds number, Grashof number, and Stefan numbers, are presented.

An Approximate Solution for Incompressible Flow About an Ellipsoid Near a Plane Wall

1950 ◽  
Vol 17 (2) ◽  
pp. 154-158
Author(s):  
Phillip Eisenberg
Keyword(s):  
Approximate Solution ◽  
Velocity Distribution ◽  
Closed Form ◽  
Incompressible Flow ◽  
Velocity Potential ◽  
Plane Wall ◽  
Wall Effect ◽  
Pressure Distributions

Abstract Using the method of successive images, an approximate solution for the velocity potential is obtained in closed form for incompressible flow about an ovary ellipsoid near a plane wall. The velocity distribution is computed from this solution in two ways. The first computation properly predicts differences in velocities on opposite half-meridians of the ellipsoid. A second method results in a symmetric velocity distribution but is useful for rapid estimates of the average wall effect. Pressure distributions calculated by this theory are compared with values measured on 4:1 and 6:1 ellipsoid models.

Rounded Fin Edge and Step Position Effects on Discharge Coefficient in Rotating Labyrinth Seals

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Andrea Rapisarda ◽  
Alessio Desando ◽  
Elena Campagnoli ◽  
Roberto Taurino
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Leading Edge ◽  
Experimental Tests ◽  
Velocity Profiles ◽  
Pollutant Emission ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Position Effects ◽  
Impact Reduction

The design of modern aircrafts propulsion systems is strongly influenced by the important objective of environmental impact reduction. Through a great number of researches carried out in the last decades, significant improvements have been obtained in terms of lower fuel consumption and pollutant emission. Experimental tests are a necessary step to achieve new solutions that are more efficient than the current designs, even if during the preliminary design phase, a valid alternative to expensive experimental tests is the implementation of numerical models. The processing power of modern computers allows indeed the simulation of more complex and detailed phenomena than the past years. The present work focuses on the implementation of a numerical model for rotating stepped labyrinth seals installed in low-pressure turbines. These components are widely employed in sealing turbomachinery to reduce the leakage flow between rotating components. The numerical simulations were performed by using computational fluid dynamics (CFD) methodology, focusing on the leakage performances at different rotating speeds and inlet preswirl ratios. Investigations on velocity profiles into seal cavities were also carried out. To begin with, a smooth labyrinth seal model was validated by using the experimental data found in the literature. The numerical simulations were extended to the honeycomb labyrinth seals, with the validation performed on the velocity profiles. Then, the effects of two geometrical parameters, the rounded fin tip leading edge, and the step position were numerically investigated for both smooth and honeycomb labyrinth seals. The obtained results are generally in good agreement with the experimental data. The main effect found when the fin tip leading edge was rounded was a large increase in leakage flow, while the step position contribution to the flow path behavior is nonmonotone.

ASSESSMENT OF MULTALL AS CFD CODE FOR THE ANALYSIS OF TUBE-AXIAL FANS

2021 ◽  
pp. 1-12
Author(s):  
Piero Danieli ◽  
Massimo Masi ◽  
Giovanni Delibra ◽  
Alessandro Corsini ◽  
Andrea Lazzaretto
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Velocity Distribution ◽  
High Speed ◽  
State Of The Art ◽  
Stable Operation ◽  
Pressure Curve ◽  
Analysis Tool ◽  
Low Speed ◽  
Axial Fans

Abstract This work deals with the application of the open source CFD code MULTALL to the analysis of tube-axial-fans. The code has been widely validated in the literature for high-speed turbomachine flows but not applied yet to low speed tutbomachines. The aim of this work is to assess the degree of reliability of MULTALL as a tool for simulating the internal flow in industrial axial-flow fan rotors. To this end, the predictions of the steady-state air flow field in the annular sector of a 315 mm tube-axial fan obtained by MULTALL 18.3 are compared with those obtained by two state-of-the-art CFD codes and experimental data of the global aerodynamic performance of the fan and the pitch-wise averaged velocity distribution downstream of the rotor. All the steady-state RANS calculations were performed on either fully structured hexahedron or hexa-dominant grids using classical formulations of algebraic turbulence models. The pressure curve and the trend of the aeraulic efficiency in the stable operation range of the fan predicted by MULTALL show very good agreement with both the experimental data and the other CFD results. Although the estimation of the fan efficiency predicted by MULTALL can be noticeably improved by the more sophisticated state-of-the-art CFD codes, the analysis of the velocity distribution at the rotor exit supports the use of MULTALL as a reliable CFD analysis tool for designers of low-speed axial fans.

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