scholarly journals Penetration of vertical pulsed jets in crossflow at low velocity ratio

2021 ◽  
Vol 2119 (1) ◽  
pp. 012010
Author(s):  
K G Dobroselsky
Keyword(s):  
Velocity Ratio ◽  
Fixed Ratio ◽  
Transverse Flow ◽  
Jet Flows ◽  
Low Velocity ◽  
Pulsed Jets ◽  
Pulsed Jet ◽  
Oscillating Jet ◽  
Pulsating Jet ◽  
Jet Velocities

Abstract Using the visualization method, the initial rise and penetration of a circular turbulent pulsed jet into a transverse air flow are studied at the ratio of jet velocities to the transverse flow r = u j /u f = 0.67–2.33. A comparative assessment of the penetration of a pulsating jet into a transverse flow for frequencies from 0 to 20 Hz is carried out. The cases of both stationary and oscillating jet flows are analyzed. The penetration of a pulsating jet into a transverse flow is shown to be more significant than for a stationary one and depends on an increase in the ratio of velocities and frequency: it increases linearly at a fixed frequency and passes through a minimum at a fixed ratio of velocities.

Comparisons of Initially Turbulent, Low-Velocity-Ratio Circular and Square Coaxial Jets

AIAA Journal ◽  
2003 ◽  
Vol 41 (2) ◽  
pp. 230-239 ◽  
Author(s):  
Dimitris E. Nikitopoulos ◽  
Jason W. Bitting ◽  
Sivaram Gogineni
Keyword(s):  
Velocity Ratio ◽  
Low Velocity ◽  
Coaxial Jets

A Numerical Study of Inlet Geometry for a Low Inertia Mixed Flow Turbocharger Turbine

2014 ◽  
Author(s):  
Thomas M. Leonard ◽  
Stephen Spence ◽  
Juliana Early ◽  
Dietmar Filsinger
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Velocity Ratio ◽  
Cone Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transient Performance ◽  
Blade Angle ◽  
Low Velocity ◽  
Mixed Flow

Mixed flow turbines can offer improvements over typical radial turbines used in automotive turbochargers, with regards to transient performance and low velocity ratio efficiency. Turbine rotor mass dominates the rotating inertia of the turbocharger, and any reductions of mass in the outer radii of the wheel, including the rotor back-disk, can significantly reduce this inertia and improve the acceleration of the assembly. Off-design, low velocity ratio conditions are typified by highly tangential flow at the rotor inlet and a non-zero inlet blade angle is preferred for such operating conditions. This is achievable in a Mixed Flow Turbine without increasing bending stresses within the rotor blade, which is beneficial in high speed and high inlet temperature turbine design. A range of mixed flow turbine rotors was designed with varying cone angle and inlet blade angle and each was assessed at a number of operating points. These rotors were based on an existing radial flow turbine, and both the hub and shroud contours and exducer geometry were maintained. The inertia of each rotor was also considered. The results indicated that there was a trade-off between efficiency and inertia for the rotors and certain designs may be beneficial for the transient performance of downsized, turbocharged engines.

Influence of Inlet Velocity Ratio on the Outlet Flow Uniformity of a Fan-Shaped Film Cooling Hole

2009 ◽  
Author(s):  
James S. Porter ◽  
Alan D. Henderson ◽  
Gregory J. Walker
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Velocity Ratio ◽  
Internal Flow ◽  
Experimental Investigations ◽  
Low Velocity ◽  
Inlet Velocity ◽  
Cooling Hole ◽  
Outlet Flow ◽  
Inlet Conditions

Literature regarding the influence of inlet conditions on cooling hole flows is reviewed. A general failure to fully quantify inlet conditions and an inconsistent terminology for describing them is noted. This paper argues for use of an inlet velocity ratio (IVR) defined as the ratio of the coolant passage velocity to the jet velocity, together with additional parameters required to define the velocity distribution in the coolant supply passage. Large scale experimental investigations of the internal flow field for a laterally expanded 50 times scale fan-shaped hole are presented, together with a computational investigation of the flow, for three inlet velocity ratios. Inlet lip separation causes a jetting effect that extends throughout the length of the cooling hole. A low velocity region of separated fluid exists on the downstream wall of the diffuser which deflects the jetting fluid towards the upstream side of the hole. This effect is most pronounced at low IVR values. The exit velocity profiles and turbulence distributions are highly dependent on the IVR.

Heat Transfer Characteristics of Non-Uniform Flow Around a Circular Cylinder in a T-Junction Duct

2020 ◽  
Author(s):  
Xiaoyu Wang ◽  
Di Qi ◽  
Tong Li ◽  
Mei Lin ◽  
Hanbing Ke ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Velocity Ratio ◽  
Correlation Coefficients ◽  
Heat Transfer Characteristics ◽  
Low Velocity ◽  
Stagnation Points ◽  
Transfer Characteristics ◽  
Low Speed Wind Tunnel ◽  
Straight Duct

Abstract Heat transfer characteristics of a circular cylinder in the branch of a T-junction are experimentally investigated in a low-speed wind tunnel with Reynolds number of Rec = 9163. Local and average heat transfer distributions around the circular cylinder are obtained for the cylinder positions from x/Dh=0.5 to 13 and the velocity ratios from 0.117 to 0.614. It is found that the overall heat transfer characteristics in a T-junction duct at high velocity ratio are lower than those at low velocity ratio, and both are higher than those in the straight duct. The local Nusselt number in the T-junction duct is asymmetrical distribution and weakens with increasing velocity ratios and positions of the cylinder. The angles of the front and rear stagnation points in the T-junction duct are the same as those in the straight duct at certain velocity ratio and/or position of the cylinder. However, the angles of the front and rear separation points in the T-junction duct do not match those in the straight duct. Both the heat transfer correlation coefficients and the amplitude ratios increase with increasing positions of the circular cylinder and velocity ratios.

Optimal Vortex Ring Formation: A Study of Vortex Ring Formation in Starting and Pulsed Jets (Keynote)

2003 ◽  
Author(s):  
Morteza Gharib
Keyword(s):  
Vortex Ring ◽  
Basic Element ◽  
Ring Formation ◽  
Nozzle Diameter ◽  
Vortex Rings ◽  
Jet Flows ◽  
Ambient Fluid ◽  
Pulsed Jets ◽  
Vortex Ring Formation ◽  
Maximization Principle

Pulsatile jet flows are found in many industrially relevant fluid mechanical problems. A common feature of these flows is that they are fundamentally a series of fluid pulses. This aspect of pulsatile jets implies vortex rings are a basic element of the resulting flow. The significance of this observation is based in part on the tendency of vortex rings to entrain ambient fluid during their formation, but more so on the recent discovery of the phenomenon of vortex ring pinch off. This phenomenon was characterized for starting jets (individual pulses) showing that for pulses sufficiently long with respect to the nozzle diameter (i.e., sufficiently large L/D), the vortex ring stops forming and pinches off from the generating jet. This represents a maximization principle for vortex ring formation and suggests that any effects associated with vortex ring formation in pulsatile jets (e.g., enhanced entrainment), might be able to be optimized by properly selecting the L/D for each pulse.

Azimuthal asymmetry of a point source in a cylindrical low velocity medium

1962 ◽  
Vol 52 (1) ◽  
pp. 139-144
Author(s):  
W. C. Meecham ◽  
John DeNoyer
Keyword(s):  
Point Source ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Azimuthal Asymmetry ◽  
Low Density ◽  
Low Velocity ◽  
Frequency Dependent ◽  
Fluid Medium

Abstract The geometry of the medium in the vicinity of an otherwise symmetrical source is shown to produce a frequency dependent variation of amplitude with azimuth. The model considered is a cylindrical low velocity and low density fluid medium that is contained in a full space of a higher velocity and density fluid material. A simple harmonic point source is located on the axis of the cylinder. Amplitudes in the higher velocity medium at large distances from the source are found to be functions of the velocity ratio and the density ratio of the two media, the radius of the cylinder, the wavelength, and the angle between the axis of the cylinder and a line connecting the point of observation with the source.

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