Biorheology (Part I) & Numerical Investigation of Flow-Induced Vibration (Part II)
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This Master’s thesis work is composed of two research categories. The first part seeks to develop a better understanding of the rheological properties of platelet-rich plasma (PRP), a blood-derived product used as a therapy for osteoarthritis and tendon injuries and the second part aims at evaluation of the flow-induced vibration (FIV) within a subsea choke valve. Blood-derived products, particularly PRP, have received increased attention in the past several years due to their great potential as a therapy for osteoarthritis and tendon injuries. Therefore, characterizing the mechanical properties of PRP becomes important to better understand its therapeutic efficacy. Rheological characterization of PRP provides further insight into its mechanism of action. Flow-sweep, Small Amplitude Oscillatory Shear (SAOS), Large Amplitude Oscillatory Shear (LAOS), and thixotropy tests have been performed at room and physiological temperatures to characterize the non-Newtonian properties of PRP samples. Flow-sweep tests reveal shear-thinning behavior (also observed in LAOS experiments), with higher apparent viscosity observed at temperature. Rheological models such as Carreau, Casson, power-law, and Herschel-Bulkley have been fitted to the flow-sweep data with the latter showing the closest agreement. The calculated boundaries of low/high-shear rates in flow-sweep tests as well as minimum-torque, sample-inertia, and instrument-inertia limits in SAOS frequency-sweep experiments are correspondingly provided for accurate interpretation of the results. Although, the window of interpretable SAOS results is found to be narrow. Furthermore, the non-linear and transient viscoelasticity is quantified with the help of the LAOS tests. The thixotropic behavior of PRP solutions is further quantified through the peak-hold test, and further compared against the results of whole blood previously published in the literature. Part two of the thesis investigates a wellhead choke valve, a type of control valve, which is mostly used to control the flow and pressure of fluids from a reservoir in an oil and gas production. A numerical study is performed using STAR-CCM+ software to study and visualize the complex physics of the compressible flow in question. Our study is carried out on a subsea choke valve model obtained from Master Flo Valve (USA) Inc., FIV investigation on dominant frequency modes within the flow has been conducted using fast-Fourier transform (FFT). The dominant frequency is then compared against the experimental natural frequency of vibration of the valve assembly to assess the risk of resonance and mechanical failure. To complement the FFT analysis, the Mach number, pressure, and temperature contours have been presented on three orthogonal planes within the valve.