This article describes the time dependent FLOW of a non-Newtonian fluid with heat transfer. We consider three dimensional unsteady FLOW and heat transfer of an Oldroyd-B fluid for CONSTANT temperature (CT) and CONSTANT heat flux (CH) cases over an unsteady bidirectional stretching surface. Homotopic solutions of the governing boundary value problems have been computed. Convergence for both velocity and temperature profiles is explored. The effects of emerging parameters on the velocity and temperature fields are investigated with the help of graphs and tabular data. It is observed that due to unsteadiness temperature in both the CONSTANT temperature and CONSTANT heat flux cases decrease significantly. Comparison of obtained and previously published results is found in excellent agreement.

Measuring the volume of a bubble, especially at its detachment, is a basic subject in gas-liquid two-phase FLOW research. A new indirect method for this measurement under CONSTANT FLOW conditions is presented. An electronic device is designed and constructed based on laser beam intensity. This device calculates the frequency of the bubble formation by measuring the total time of the formation process and counting the number of bubbles crossing the laser beam. The bubble volume at detachment can be calculated by dividing the volumetric FLOW rate of air by the frequency of bubble formation. The latter and the bubble volume at detachment are measured for three different heights of water above the tip of the orifice (50, 100, and 150 mm), three orifice diameters (1, 2, and 3 mm), and different gas FLOW rates between 2000 and 10000 ml/hr. Comparing and validating the results with the results of the image processing (IP) method and the correlations presented by other studies shows the strong accuracy of the present method.

Heat transfer enhancement has been the goal of many researches carried out over the past three decades. Employing the modified fluids, changing the FLOW geometry, and active methods are among the commonly used techniques. The effects of three referred techniques, employing pulsation FLOW as active method, nanofluids instead of conventional fluid as modified fluids and helical-coil tube as changing the FLOW geometry on the fluid FLOW and heat transfer have been investigated numerically. The results of interests with pulsation FLOW and non-pulsation FLOW have been presented. In this research, the results indicated that, the coil pitch tube and coil diameter have a minor effect on the Nusselt number (5 and 7%, respectively). But the Reynolds number has a major effect on the Nusselt number, so that by increasing the Reynolds number from 5000 to 100000, the Nusselt number will be enhanced by more than 200%. The nanofluid pressure drop and heat transfer coefficient increased with nanoparticles volume fraction. In addition, by introducing a concept as the performance evaluation criteria, the mutual effects of the pressure drop and Nusselt number were investigated with referred concept. Performance evaluation criteria revealed that employing the nanofluid in lower Reynolds numbers yields higher effects on the fluid FLOW and heat transfer.

The similarity solution of the steady-state motion and heat transfer of a viscous incompressible fluid contained between two concentric spheres, maintained at different temperatures and rotating about a common axis with different CONSTANT angular velocities is considered. The resulting FLOW pattern, temperature distribution and heat transfer characteristics are presented for various cases. Aside from the energy equation, the same results as previous works are obtained for Navier-Stokes equations, but with less computational complexities.

This paper presents an analytical model characterizing unsteady groundwater FLOW in an unconfined aquifer resting on a sloping impervious bed. The aquifer is in contact with a CONSTANT water level at one end. The other end is connected to a stream whose level is increasing form an initial level to a final level at a known exponentially decaying function of time. Moreover, the aquifer is replenished by a CONSTANT downward recharge. The linearized Boussinesq equation is solved analytically using Laplace transform technique to obtain the closed form expression for hydraulic head and FLOW rate at the stream-aquifer interface. The expressions derived in this study can also handle the cases of upward sloping, horizontal bed conditions and sudden rise in stream water. The validity of linearization method adopted in this study is examined by solving the nonlinear equation by an explicit numerical scheme. Response of an aquifer to the variations in bed slope, recharge rate and rise rate of the stream water is illustrated with a numerical example. Sensitivity of the FLOW rate with various parameters is analyzed.