Study on Impingement of Air Jet from Orifice on Convex Surface for Unconfined Flow

Experiments are performed to study surface curvature effects on the impingement cooling flow and the heat transfer processes over a concave and a convex surface. A single air jet issuing from different size slots continuously impinges normally on the concave side or the convexside of a heated semicylindrical surface. An electrical resistance wire is used to generate smoke, which allows us to visualize the impinging flow structure. The local heat transfer Nusselt number along the surfaces is measured. For impingement on a convex surface, three-dimensional counterrotating vortices on the stagnation point are initiated, which result in the enhancement of the heat transfer process. For impingement on a concave surface, the heat transfer Nusselt number increases with increasing surface curvature, which suggests the initiation of Taylor–Go¨rtler vortices along the surface. In the experiment, the Reynolds number ranges from 6000 to 350,000, the slot-to-plate spacing from 2 to 16, and the diameter-to-slot-width ratio D/b from 8 to 45.7. Correlations of both the stagnation point and the average Nusselt number over the curved surface, which account for the surface curvature effect, are presented.

Download Full-text

A Note on the Mixing Process in the Flow Induced by a High Velocity Air Jet

Journal of the Royal Aeronautical Society ◽

10.1017/s0368393100132948 ◽

1957 ◽

Vol 61 (561) ◽

pp. 631-633 ◽

Cited By ~ 1

Author(s):

J. Black

Keyword(s):

Flow Separation ◽

High Velocity ◽

Convex Surface ◽

Mixing Process ◽

Low Velocity ◽

Trailing Edge ◽

Air Jet ◽

Air Stream ◽

Considerable Length ◽

Trailing Edge Flap

It is well known that when a plane air jet of high velocity blows over a convex surface, such as the upper surface of a lowered trailing edge flap, it flows along the surface, remaining attached for a considerable length; in the case of the flap, it adheres right to the trailing edge. This effect, usually described as the Coanda effect, has been utilised in the attempts to increase lift at constant incidence by “flap-blowing” in which the high velocity air jet is ejected either through slots in the flap shroud, or tangentially out of the flap surface.The low velocity air stream approaching the flap over the wing upper surface, which in the absence of “blowing” would tend to separate at the flap shroud, is entrained by the high velocity jet, and the incipient flow separation over the flap thereby suppressed. The energy contained in the “blowing” jet can, in addition, also produce “supercirculation.“

Download Full-text

The Consequence of Target Surface Curvature in the Jet Impingement Cooling

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.766-767.1148 ◽

2015 ◽

Vol 766-767 ◽

pp. 1148-1152

Author(s):

M. Karthigairajan ◽

S. Mohanamurugan ◽

K. Umanath

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Convex Surface ◽

Heated Surface ◽

Jet Impingement ◽

Target Surface ◽

Uniform Heat Flux ◽

Impingement Cooling ◽

Air Jet ◽

Increase With Increase

An experiment sturdy has been carried out for jet impingement cooling on the spherically convex surface is the development of mechanism. The effect of curvature, Space between jet exit and target surface, and Reynolds number on heat transfer is investigated for around air jet on hemispherical surface. The flow at the jet exit has fully developed velocity profile. A uniform heat flux boundary is created on the heated surface. The experiments are performed for 5000<Re<25000, 2<L/d<10, and jet diameters ranging from 1.3, 2.1, 3.4, 4.0 and 5.2 cm. In the mean time effect of curvature on local heat transfer is negligible at the wall jet region corresponding to r/d>0.5. From the experimental results the variation of the D/d ratio with local Nusselt number (Nust) for various Reynolds numbers and various L/d ratios are plotted. The results show that Nust increase with increase in curvature and the effect of the curvature will high at high Reynolds number. i.e. Nust at Re=25000 is 25% higher than at Re= 5000 This may be attributed to an increase in curvature increases acceleration, & size of three dimensional counter rotating vortices at stagnation point and the increment of Reynolds number increases the jet momentum, and also enhances the vortices creation. Nust is peaking in the L/d ratio of 6 because of high turbulence intensity as this distance.

Download Full-text

Effect of orifice geometry and orifice to test section spacing on distribution of wall static pressure on a convex surface

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.13.2.2019.05.0402 ◽

2019 ◽

Vol 13 (2) ◽

pp. 4835-4845

Author(s):

Anilkumar M. Hanchinal ◽

Vadiraj V. Katti

Keyword(s):

Test Section ◽

Smooth Surface ◽

Static Pressure ◽

Convex Surface ◽

Pressure Coefficient ◽

Jet Impingement ◽

Surface Distance ◽

Air Jet ◽

Geometric Conditions ◽

Maximum Value

The experimental investigation is carried out to study the distribution of wall static pressure (Cp & Cpo) on the convex smooth surface by air jet impingement. A great deal of attention was paid to analyze the effects of orifice geometry for various flow and geometric conditions, a comparison of the wall static pressure coefficient is done for different orifice. The experimental results show that the wall static pressure on a convex test section is higher for rectangular orifice compared to other orifice. The wall static pressure decreases circumferentially from its maximum value at the stagnation point (θ = 0°) and also for higher Z/dh. Higher value of Cp and Cpo are obtained for unconfined flow. The experiments were performed with the following parameters: the jet Reynolds number (Re) = 10000–50000, the orifice-to- convex surface distance (Z/dh) = 1–5, Circumferential angle (θ) = 0° to 30°, Curvature ratio (D/dh), Orifice = Circular, Square, Triangle, Rectangle.

Download Full-text

Dependence of the joint configuration on the dynamic immobility fulcrum

Russian Osteopathic Journal ◽

10.32885/2220-0975-2019-1-2-108-114 ◽

2019 ◽

pp. 108-114

Author(s):

A. D. Kozlov ◽

Yu. P. Potekhina

Keyword(s):

Kinetic Energy ◽

Convex Surface ◽

The Other ◽

Concave Surface ◽

Joint Configuration ◽

Articular Surfaces

Although joints with synovial cavities and articular surfaces are very variable, they all have one common peculiarity. In most cases, one of the articular surfaces is concave, whereas the other one is convex. During the formation of a joint, the epiphysis, which has less kinetic energy during the movements in the joint, forms a convex surface, whereas large kinetic energy forms the epiphysis with a concave surface. Basing on this concept, the analysis of the structure of the joints, allows to determine forces involved into their formation, and to identify the general patterns of the formation of the skeleton.

Download Full-text