Three-dimensional flow of Newtonian and Boger fluids in square-square contractions

The flow of a Newtonian fluid and a Boger fluid through sudden square–square contractions was investigated experimentally aiming to characterize the flow and provide quantitative data for benchmarking in a complex three-dimensional flow. Visualizations of the flow patterns were undertaken using streakline photography, detailed velocity field measurementswere conducted using particle image velocimetry (PIV) and pressure drop measurements were performed in various geometries with different contraction ratios. For the Newtonian fluid, the experimental results are compared with numerical simulations performed using a finite volume method, and excellent agreement is found for the range of Reynolds number tested (Re2 ≤23). For the viscoelastic case, recirculations are still present upstream of the contraction but we also observe other complex flow patterns that are dependent on contraction ratio (CR) and Deborah number (De2) for the range of conditions studied: CR = 2.4, 4, 8, 12 and De2 ≤150. For low contraction ratios strong divergent flow is observed upstream of the contraction, whereas for high contraction ratios there is no upstream divergent flow, except in the vicinity of the re-entrant corner where a localized a typical divergent flow is observed. For all contraction ratios studied, at sufficiently high Deborah numbers, strong elastic vortex enhancement upstream of the contraction is observed, which leads to the onset of a periodic complex flow at higher flow rates. The vortices observed under steady flow are not closed, and fluid elasticity was found to modify the flow direction within the recirculations as compared to that found for Newtonian fluids. The entry pressure drop, quantified using a Couette correction, was found to increase with the Deborah number for the higher contraction ratios

Experimental Design and Setup of Circulation Flow Loop - Using Particle Image Velocimetry

Master's thesis in Petroleum engineeringMud left static in a well over a longer period of time can begin to gel up or form filter cakes along the formation wall and in washout zones, which can be difficult to remove. Therefore, proper mud mobilization and removal is necessary to ensure a good zonal isolation prior to primary cementing. The Bingham plastic rheology model is widely used by mud engineers to mathematically describe the rheological behavior of drilling fluids. The equation for circulation efficiency is directly related to the fluid velocity profile equations. Relevant theory is introduced before experimentation and results are presented. The experimental work in this thesis is based on a field size mud conditioning operation. The annular geometry between a 95/8-in casing and a 121/4-in borehole is scaled down to laboratory size and configured as a slot for experimental purposes. Accompanying mud rheology and conditioning pump rate is scaled down by the Bingham number similarity method. Particle image velocimetry (PIV) experiments were conducted on an acrylic flow channel for a Newtonian fluid to study the velocity profile. An aspect ratio of 1:10 was found to be acceptable to neglect the sidewall effects when measuring the velocity profile 8,5 centimeters from the wall, both from theoretical solutions and by comparing with experimental results. Carbopol dispersed in an aqueous solution was found to be the most promising yield stress fluid for the future non-Newtonian PIV experiments. Despite being described better by the Herschel-Bulkley rheology model rather than the Bingham plastic model, its rheology was found to be acceptable by comparing the velocity profiles generated by the regression parameters by the two rheology models Both analytical solutions and MATLAB were used to verify the aspect ratio and feasibility of moving on with Carbopol.submittedVersio

Forced Convective Heat Transfer and Fluid Flow Characteristics in Curved Ducts

Fluid flow through curved ducts is influenced by the centrifugal action arising from duct curvature and has behaviour uniquely different to flow within straight ducts. In such flows, centrifugal forces induce secondary flow vortices and produce spiralling fluid motion within curved ducts. Secondary flow promotes fluid mixing with intrinsic potential for thermal enhancement and, exhibits possibility of fluid instability and additional secondary vortices under certain flow conditions. Reviewing the published work on numerical and experimental studies, this chapter discusses the current knowledge-base on secondary flow in curved ducts and, identifies the deficiencies in analyses and fundamental understanding. The chapter then presents an extensive research study capturing advanced aspects of secondary flow behaviour and associated wall heat transfer processes for both rectangular and elliptical curved ducts.This study develops a new three-dimensional numerical model incorporating helicity approach and curvilinear mesh that is validated against published data to overcome current modelling limitations. Flow patterns and thermal characteristics are obtained for a range of duct aspect ratios, flow rates and wall heat fluxes. Results are analysed for parametric influences and construed for clearer physical understanding of the flow mechanics involved. The study formulates two analytical techniques whereby secondary vortex detection is integrated into the computational process with unprecedented accuracy and reliability. The vortex inception at flow instability is carefully examined with respect to the duct aspect ratio, duct geometry and flow rate. An entropy-based thermal optimisation technique is developed and tested for fluid flow through curved rectangular and elliptical ducts

Electroosmosis modulated peristaltic biorheological flow through an asymmetric microchannel : mathematical model

A theoretical study is presented of peristaltic hydrodynamics of an aqueous electrolytic nonNewtonian Jeffrey bio-rheological fluid through an asymmetric microchannel under an applied axial electric field. An analytical approach is adopted to obtain the closed form solution for velocity, volumetric flow, pressure difference and stream function. The analysis is also restricted under the low Reynolds number assumption and lubrication theory approximations. Debye-Hückel linearization (i.e. wall zeta potential ≤ 25mV) is also considered. Streamline plots are also presented for the different electro-osmotic parameter, varying magnitudes of the electric field (both aiding and opposing cases) and for different values of the ratio of relaxation to retardation time parameter. Comparisons are also included between the Newtonian and general non-Newtonian Jeffrey fluid cases. The results presented here may be of fundamental interest towards designing lab-on-a-chip devices for flow mixing, cell manipulation, micro-scale pumps etc. Trapping is shown to be more sensitive to an electric field (aiding, opposing and neutral) rather than the electro-osmotic parameter and viscoelastic relaxation to retardation ratio parameter. The results may also help towards the design of organ-on-a-chip like devices for better drug design

Validation of a magneto- and ferro-hydrodynamic model for non-isothermal flows in conjunction with Newtonian and non-Newtonian fluids

This work focuses on the validation of a magnetohydrodynamic (MHD) and ferrohydrodynamic (FHD) model for non-isothermal flows in conjunction with Newtonian and non- Newtonian fluids. The importance of this research field is to gain insight into the interaction of non-linear viscous behaviour of blood flow in the presence of MHD and FHD effects, because its biomedical application such as magneto resonance imaging (MRI) is in the centre of research interest. For incompressible flows coupled with MHD and FHD models, the Lorentz force and a Joule heating term appear due to the MHD effects and the magnetization and magnetocaloric terms appear due to the FHD effects in the non-linear momentum and temperature equations, respectively. Tzirtzilakis and Loukopoulos [1] investigated the effects of MHD and FHD for incompressible non-isothermal flows in conjunction with Newtonian fluids in a small rectangular channel. Their model excluded the non-linear viscous behaviour of blood flows considering blood as a Newtonian biofluid. Tzirakis et al. [2, 3] modelled the effects of MHD and FHD for incompressible isothermal flows in a circular duct and through a stenosis in conjunction with both Newtonian and non-Newtonian fluids, although their approach neglects the non-isothermal magnetocaloric FHD effects. Due to the fact that there is a lack of experimental data available for non-isothermal and non-Newtonian blood flows in the presence of MHD and FHD effects, therefore the objective of this study is to establish adequate validation test cases in order to assess the reliability of the implemented non-isothermal and non-Newtonian MHD-FHD models. The non-isothermal Hartmann flow has been chosen as a benchmark physical problem to study velocity and temperature distributions for Newtonian fluids and non-Newtonian blood flows in a planar microfluidic channel. In addition to this, the numerical behaviour of an incompressible and non-isothermal non-Newtonian blood flow has been investigated from computational aspects when a dipole-like rotational magnetic field generated by infinite conducting wires. The numerical results are compared to available computational data taken from literature

Investigation Of Laminar Convective Heat Transfer And Pressure Drop Of SiO2 Nanofluid In Ducts Of Different Geometries

Engineers are seeking alternatives to conventional heat transfer fluids and in an attempt to improve their thermal transport properties, they added thermally conductive solids into the conventional fluids resulting in a fluid called nanofluid. Nanofluid was suggested as an alternative solution to the problem and many publications reported its potential for heat transfer enhancement. This thesis describes the experimental study of 9.58% by vol. silica/water nanofluid flow through different flow geometries which are circular, hexagonal and rectangular ducts of close hydraulic diameter. The experiments are performed at uniform heat flux condition. The aim of this thesis is to determine experimentally the best duct geometry for optimal thermal performance in nanofluids. The effect of the cross-section of the flow geometry on the enhancement capability of nanofluid is the focus of this research and four different geometries of relatively equal hydraulic diameters were studied. This study compares the result from the different duct geometries in order to identify the best flow channel for optimal heat transfer using nanofluids. Based on the test data, the thermal performance comparisons are made under three constraints (similar mass flow rate and Reynolds number). It was observed from the comparisons that the rectangular duct showed the highest heat transfer capability through a higher Nusselt number and heat transfer coefficients at for the silica/water nanofluid flow. The circular duct was next to the rectangular duct in thermal performance. There was no significant change in friction factor between the ducts for both water and nanofluid flow