[en] The flow of a free jet of polymer solution or melt between a nozzle supplying fluid at a constant flow rate and a takeoff device in the form of a uniformly rotating roll is studied. The exit and takeoff points (the latter being the point at which the jet touches the roll surface) are on the same level, while the jet itself lies in a vertical plane. The jet sags under gravity by an amount that depends on the tension, the fluid density, the flow zone length, and the relationship between the takeoff and exit velocities

[en] Experimental investigations have shown that the flow discharged from a centrifugal compressor or pump impeller into the diffuser is unsteady and contributes for additional losses in the diffuser. The partially parabolic method is used to calculate this flow in the diffuser and reveals the mechanism of smoothing the distorted flow downstream. Calculated results are compared with measurements and good agreement is found. (author)

[en] With the overall goal being a better understanding of the sensing environment from the local perspective of a situated agent, we studied uniform flows and Kármán vortex streets in a frame of reference relevant to a fish or swimming robot. We visualized each flow regime with digital particle image velocimetry and then took local measurements using a rigid body with laterally distributed parallel pressure sensor arrays. Time and frequency domain methods were used to characterize hydrodynamically relevant scenarios in steady and unsteady flows for control applications. Here we report that a distributed pressure sensing mechanism has the capability to discriminate Kármán vortex streets from uniform flows, and determine the orientation and position of the platform with respect to the incoming flow and the centre axis of the Kármán vortex street. It also enables the computation of hydrodynamic features which may be relevant for a robot while interacting with the flow, such as vortex shedding frequency, vortex travelling speed and downstream distance between vortices. A Kármán vortex street was distinguished in this study from uniform flows by analysing the magnitude of fluctuations present in the sensor measurements and the number of sensors detecting the same dominant frequency. In the Kármán vortex street the turbulence intensity was 30% higher than that in the uniform flow and the sensors collectively sensed the vortex shedding frequency as the dominant frequency. The position and orientation of the sensor platform were determined via a comparative analysis between laterally distributed sensor arrays; the vortex travelling speed was estimated via a cross-correlation analysis among the sensors. (paper)

[en] The problem of two-dimensional unsteady flow of a non-Newtonian fluid between two infinite porous plates has been considered in this paper. One wall is assumed to be fixed and the motion of the other wall as well as the suction velocity vary periodically with time about a non-zero constant mean. Numerical calculations have been made and the effects of the non-Newtonian parameter, frequency parameter and suction parameter have been shown on the velocity distribution, skin-friction phase and amplitude both at the moving and the stationary walls. (author)

[en] The unsteady Hele-Shaw flow of visco-elastic fluid of Kuvshinkskii type under the influence of uniform transverse magnetic field has been studied assuming the pressure gradient to be proportional to exp (-nt) and the fluid to be of small electrical conductivity with magnetic Reynolds number much less than unity so that the induced magnetic field can be neglected in comparison with the applied magnetic field. The velocity components in the Hele-Shaw cell have been evaluated and a number of results are deduced from them. The effects of magnetic parameter M and the relaxation time lambda on the velocity components u and v have been investigated. It is observed the velocity component u decreases with the increase in M or lambda whereas v increases with the increase in M or lambda. (auth.)

[en] The novel technique of particle image displacement velocimetry allows visualization of two-dimensional flows as well as the quantification of the instantaneous velocity and vorticity fields. The method's principles of operation are then presented; the method is shown to be suited to the gathering of both temporal and spatial data, as is required in the case of complex flow fields. 6 references

[en] In the context of the homogeneous model of the ocean some properties of lineary unstable flows are examined. The analysis leads to an eigenvalue confinement depending upon the vertical Ekman number and provides consequently necessary conditions for the instability in terms of the upper-surface stress

[en] Attention is drawn to conduction coupling (in the wall), convection (in the fluid) which can intrinsically distort the known convection laws relative to an infinite conductance of the wall. In the case of non-stationary or non-established convection, computer calculations can reduce the required experimental work by first picking out the influence of the parameters. As an illustration, the establishment of the stationary convection rate in straight tubes and in those with a curved inlet is dealt with, for a fluid with constant properties. It is shown how unpredictable is the complex composition of the 'intake effects' due to the geometry of the pipe, the Reynolds number and last, the Prandt number

[en] In this paper a new methodology is introduced to simulate flows around complex geometries by using overset unstructured grids. The proposed algorithm can also be used for the unsteady flows about objects in relative motions. In such a case since the elements are not deformed during the computation the costly part of conventional methods, re-meshing, is prevented. This method relies on the inter-grid boundary definition to establish communications among independent grids in the overset system. At the end, the Euler set of equations are integrated on several overset systems to examine the capabilities of this methodology. (author)

[en] The methods of measurement of the stresses induced by an unsteady fluid flow are exposed from a general point of view. They are then illustrated by examples relating to the measurement of the stresses acting on a cylinder or a pipe element