Measurements of Secondary Flows in a Rotating Duct

1972 ◽  
Vol 94 (4) ◽  
pp. 261-270 ◽  
Author(s):  
R. E. Wagner ◽  
H. R. Velkoff
Keyword(s):  
Experimental Study ◽  
Pressure Distribution ◽  
Cross Section ◽  
Experimental Work ◽  
Cross Flow ◽  
Secondary Flows ◽  
Working Fluid ◽  
Longitudinal Vortices ◽  
Developing Flow ◽  
Analytical Work

The paper presents a review of analytical and experimental work which has been done on flows in rotating ducts. It presents the results of an experimental study to measure the secondary flows predicted by the previous analytical work. A duct of approximately 3 ft in length with a cross section of 2 × 5 in. was rotated up to speeds of 300 rpm. Air was used as the working fluid. Static pressures, total pressures, and yaw angles were measured at selected points along the channel. The flow regime examined was the developing flow from the entrance to the exit of the channel. Examination of the data revealed the presence of two longitudinal vortices which extended the length of the channel. Pressure distribution across the height of the channel and across the width of the channel was obtained. The magnitude of the cross-flow velocities in the channel were determined and mapped. It was found that the data for various rotational speeds could be collapsed upon a single curve by dividing all data by the rotational speeds. The results of the experimental study provide solid verification for the hypothesis of longitudinal vortices in rotating ducts.

scholarly journals Mechanism of formation of Prandtl’s secondary flows of the second kind

2019 ◽  
Vol 484 (4) ◽  
pp. 420-425
Author(s):  
N. V. Nikitin ◽  
V. O. Pimanov ◽  
N. V. Popelenskaya
Keyword(s):  
Turbulent Flow ◽  
Cross Section ◽  
Physical Interpretation ◽  
Nonlinear Interaction ◽  
Longitudinal Component ◽  
Secondary Flows ◽  
Mechanism Of Formation ◽  
Longitudinal Vortices ◽  
Turbulent Pulsations

Turbulent flow in a tube of square cross section is investigated numerically. The concentrated longitudinal vortices responsible for the occurrence of secondary flows are studied. It is shown that the longitudinal vortices are formed as a result of nonlinear interaction of turbulent pulsations in which the pulsations of the longitudinal component of vorticity are specially adjusted in phase with the pulsations of the longitudinalvelocity component. A physical interpretation of this mechanism is given.

Equilibrium shape and stability of a liquid cylinder in cross flow at low Weber numbers

1982 ◽  
Vol 116 ◽  
pp. 393-409 ◽  
Author(s):  
D. Weihs ◽  
I. Frankel
Keyword(s):  
Pressure Distribution ◽  
Cross Section ◽  
Gas Flow ◽  
Dynamic Pressure ◽  
Equilibrium Shape ◽  
Circular Cross Section ◽  
Cross Flow ◽  
Two Factors ◽  
Break Up ◽  
The Stability

The cross-section shape and stability of a liquid cylinder moving perpendicularly to its axis in a gaseous medium is studied. Such liquid cylinders are formed during the break-up process of thin, rapidly moving liquid sheets, appearing in spray and atomization processes. The equilibrium shape is affected mainly by two factors: the dynamic-pressure distribution in the gas flow and the surface tension on the liquid boundary. The former tends to distort the liquid cross-section into an oval shape while the latter tends to restore the circular cross-section.A series expansion for the shape of the cylinder cross-section was determined by assuming incompressible potential flow, neglecting the effects of body forces and internal circulation in the liquid.The stability analysis shows that in the range of low Weber numbers the cylinder break-up is due to the divergence of varicose perturbations. The wavenumber of the most rapidly growing perturbation, its rate of growth and the maximal wavenumber for which varicose instability occurs, are all found to decrease as the Weber number grows, owing to a pressure distribution caused by the varicose distortion, which tends to reduce these perturbations.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

Effects of alternating elliptical chamber on jet impingement heat transfer in vane leading edge under different cross-flow conditions

2021 ◽  
pp. 1-17
Author(s):  
K. Xiao ◽  
J. He ◽  
Z. Feng
Keyword(s):  
Heat Transfer ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Leading Edge ◽  
Longitudinal Vortices ◽  
Impingement Jet ◽  
Flow And Heat Transfer ◽  
Impingement Heat Transfer ◽  
Cross Flow Velocity ◽  
The Cross

ABSTRACT This paper proposes an alternating elliptical impingement chamber in the leading edge of a gas turbine to restrain the cross flow and enhance the heat transfer, and investigates the detailed flow and heat transfer characteristics. The chamber consists of straight sections and transition sections. Numerical simulations are performed by solving the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes (RANS) equations with the Shear Stress Transport (SST) k– $\omega$ turbulence model. The influences of alternating the cross section on the impingement flow and heat transfer of the chamber are studied by comparison with a smooth semi-elliptical impingement chamber at a cross-flow Velocity Ratio (VR) of 0.2 and Temperature Ratio (TR) of 1.00 in the primary study. Then, the effects of the cross-flow VR and TR are further investigated. The results reveal that, in the semi-elliptical impingement chamber, the impingement jet is deflected by the cross flow and the heat transfer performance is degraded. However, in the alternating elliptical chamber, the cross flow is transformed to a pair of longitudinal vortices, and the flow direction at the centre of the cross section is parallel to the impingement jet, thus improving the jet penetration ability and enhancing the impingement heat transfer. In addition, the heat transfer in the semi-elliptical chamber degrades rapidly away from the stagnation region, while the longitudinal vortices enhance the heat transfer further, making the heat transfer coefficient distribution more uniform. The Nusselt number decreases with increase of VR and TR for both the semi-elliptical chamber and the alternating elliptical chamber. The alternating elliptical chamber enhances the heat transfer and moves the stagnation point up for all VR and TR, and the heat transfer enhancement is more obvious at high cross-flow velocity ratio.

Experimental study of breaking wave loads on elevated pile cap with rectangular cross-section

2021 ◽  
Vol 227 ◽  
pp. 108878
Author(s):  
Jie Hong ◽  
Kai Wei ◽  
Zhonghui Shen ◽  
Bo Xu ◽  
Shunquan Qin
Keyword(s):  
Experimental Study ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Breaking Wave ◽  
Wave Loads ◽  
Pile Cap
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