A. Ramachandra Rao

Influence of Lateral Walls on Peristaltic Flow in a Rectangular Duct

The flow of a viscous fluid due to symmetric peristaltic waves propagating on the horizontal sidewalls of a rectangular duct is studied under the assumptions of long wavelength and low Reynolds number. The effect of aspect ratio

Pulsatile flow in tubes of varying cross-sections

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Heat transfer in a MHD flow between eccentric disks rotating at different speeds

, ratio of height to width, on the pumping characteristics is discussed in detail. The results are compared to with those corresponding to Poiseuille flow.

Flow between torsionally oscillating disks rotating about different axes at different speeds

SummaryThe pulsatile flow of an incompressible viscous fluid in a cylindrical tube of varying cross section is investigated for small Reynolds numbers. The solutions consist of a stedy and an oscillatory part. The shear stress distribution on the wall is evaluated and discussed in detail for special geometries like tapered tubes, locally constricted tubes and peristaltic tubes. The existence of separation in the flow field is noticed.ZusammenfassungEs wird die pulsierende Strömung einer zähen inkompressiblen Flüssigkeit in Rohren mit veränderlichem Querschnitt bei kleinen Reynoldsschen Zahlen untersucht. Die Lösungen bestehen aus einem stationären und einem oszillatorischen Anteil. Die Schubspannungsverteilung an den Rohrwänden wird für einige besondere geometrische Rohrformen wie konische Rohre, örtlich eingeschnürte Rohre und peristaltische Rohre berechnet und ausführlich diskutiert. Bei einigen Fällen wird die Existenz einer Ablösung im Strömungsfeld festgestellt.

Unsteady Motion of a Stratified Rotating Viscous Fluid between Two Disks

Heat transfer in a MHD flow between two infinite eccentric disks rotating with different speeds is considered when the plates are maintained at different temperatures. The results for the corresponding nonmagnetic case presented wrongly by Banerjee and Borkakati [7] are corrected. It is observed that the eccentric rotation reduces the heat transfer on the disks.Heat transfer in a MHD flow between two infinite eccentric disks rotating with different speeds is considered when the plates are maintained at different temperatures. The results for the corresponding nonmagnetic case presented wrongly by Banerjee and Borkakati [7] are corrected. It is observed that the eccentric rotation reduces the heat transfer on the disks.ZusammenfassungDer Wärmeübergang in MHD-Strömung wird untersucht zwischen zwei unendlichen exzentrischen Platten, die mit verschiedenen Geschwindigkeiten rotieren und verschiedene Temperaturen haben. Die Ergebnisse im nichtmagnetischen Fall bringen eine Richtigstellung der von Banerjee und Borkakati [7] gefundenen Resultate. Man beobachtet eine Abnahme des Wärmeüberganges bei der exzentrischen Rotation.

Pulsatile flow of a viscous fluid in elliptical pipe of variable cross-section

The flow of an incompressible viscous fluid confined between two parallel infinite disks performing torsional oscillations with the same frequency, but rotating about different axes with different speeds has been studied. The solutions are presented for the symmetric and asymmetric first harmonic and steady streaming. The interesting features of the symmetric and asymmetric flow are discussed for the cases of small and large Womersley parameter at different ratios of the rotation speeds. The forces acting on one of the disks are also calculated.ZusammenfassungIn der vorliegenden Arbeit wird die Strömung einer zwischen zwei parallelen, unendlichen Scheiben begrenzten, inkompressiblen, viskosen Flüssigkeit untersucht; die zwei Scheiben führen Torsionsschwingungen gleicher Frequenz aus, drehen sich aber um verschiedene Achsen mit verschiedenen Geschwindigkeiten. Lösungen werden gegeben für die symmetrische und asymmetrische, erste harmonische Oberschwingung und die stationäre Strömung. Die interessanten Eigenschaften der symmetrischen und asymmetrischen Strömung werden diskutiert für die Fälle von kleinem und großem Womersley-Parameter bei verschiedenen Verhältnissen der Drehgeschwindigkeiten. Außerdem werden die Kräfte berechnet, die auf eine der Scheiben einwirken.The flow of an incompressible viscous fluid confined between two parallel infinite disks performing torsional oscillations with the same frequency, but rotating about different axes with different speeds has been studied. The solutions are presented for the symmetric and asymmetric first harmonic and steady streaming. The interesting features of the symmetric and asymmetric flow are discussed for the cases of small and large Womersley parameter at different ratios of the rotation speeds. The forces acting on one of the disks are also calculated.

Surface waves in a rotating fluid due to sources and internal boundaries@@@Oberflchenwellen in einer rotierenden Flssigkeit als Folge von Quellen und Randbedingungen

The effect of stratification is investigated on the time-dependent motion of a viscous fluid between two infinite rotating disks. Exact solutions are given for the linearized equations under Boussinesq approximation. The steady solutions of this problem obtained by Niimi (J. Phys. Soc. Japan 31 (1971) 1567) are criticized and the correct solutions are presented as a limiting case of our results when t →∞. The velocity and temperature distributions are discussed in detail for small Ekman numbers.

Time-dependent flows of rotating and stratified fluids in geometries with non-uniform cross-sections

The pulsatile flow of an incompressible viscous fluid in an elliptical pipe of slowly varying cross-section is considered. Asymptotic series solutions for the velocity distribution and pressure gradient are obtained in terms of Mathieu functions for a low Reynold number flow in which the volume flux is prescribed. An expression for shear stress on the boundary is derived. The physically significant quantities governing the flow are computed numerically and analysed for different types of constrictions. The effect of eccentricity and Womerslay parameter on the flow is discussed.

Peristaltic transport of a Newtonian fluid in an asymmetric channel

SummaryThe problem of surface waves generated by an oscillatory point source oscillating with frequency ω in a fluid rotating with constant angular velocity Ω has been investigated. The Greens function solution is obtained for an unbounded region and a region bounded internally by a circular cylinder using an appropiate Fourier transform. It is seen that in the case when ω>2Ω, the surface waves are similar to the ones existing in a potential flow but when ω<2Ω, the surface waves correspond to the inertial waves which are generated entirely due to rotation and have no counterpart in a non-rotating fluid motion.ZusammenfassungEs wird das Problem der Erzeugung von Oberflächenwellen durch eine oszillierende Punktquelle (Frequenz ω) in einer rotierenden Strömung (Winkelgeschwindigkeit Ω) untersucht. Die Greensche Funktion wird für einen unbegrenzten Bereich sowie für das Äußere eines Kreiszylinders durch eine geeignete Fouriertransformation hergeleitet. Für ω>2Ω sind die Oberflächenwellen ähnlich denen einer Potentialströmung, für ω<2Ω ergeben sich Wellen, die vollständig durch die Drehbewegung bedingt sind und die kein Gegenstück im nichtrotierenden Fall besitzen.

Peristaltic transport of a power-law fluid in a porous tube

Unsteady rotating and stratified flows in geometries with non-uniform cross-sections are investigated under Oseen approximation using Laplace transform technique. The solutions are obtained in closed form and they reveal that the flow remains oscillatory even after infinitely large time. The existence of inertial waves propagating in both positive and negative directions of the flow is observed. When the Rossby or Froude number is close to a certain infinite set of critical values the blocking and back flow occur and the flow pattern becomes more and more complicated with increasing number of stagnant zones when each critical value is crossed. The analogy that is observed in the solutions for rotating and stratified flows is also discussed.