A moving control volume approach to computing hydrodynamic forces and torques on immersed bodies

We present a moving control volume (CV) approach to computing hydrodynamic forces and torques on complex geometries. The method requires surface and volumetric integrals over a simple and regular Cartesian box that moves with an arbitrary velocity to enclose the body at all times. The moving box is aligned with Cartesian grid faces, which makes the integral evaluation straightforward in an immersed boundary (IB) framework. Discontinuous and noisy derivatives of velocity and pressure at the fluid-structure interface are avoided and far-field (smooth) velocity and pressure information is used. We re-visit the approach to compute hydrodynamic forces and torques through force/torque balance equation in a Lagrangian frame that some of us took in a prior work (Bhalla et al., J Comp Phys, 2013). We prove the equivalence of the two approaches for IB methods, thanks to the use of Peskin's delta functions. Both approaches are able to suppress spurious force oscillations and are in excellent agreement, as expected theoretically. Test cases ranging from Stokes to high Reynolds number regimes are considered. We discuss regridding issues for the moving CV method in an adaptive mesh refinement (AMR) context. The proposed moving CV method is not limited to a specific IB method and can also be used, for example, with embedded boundary methods

Minimal Exit Trajectories with Optimum Correctional Manoeuvres

Minimal exit trajectories with optimum correctional manoeuvers to a rocket between two coplaner, noncoaxial elliptic orbits in an inverse square gravitational field have been investigated. Case of trajectories with no correctional manoeuvres has been analysed. In the end minimal exit trajectories through specified orbital terminals are discussed and problem of ref. (2) is derived as a particular case

Expeditious synthetic route to B-ring functionalised 2-oxa-steroids: Synthesis of 17-ethylenedioxy-6a-hydroxy-2-oxa-4-androsten-3-one as key synthon

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OBSERVATION OF AN ISOKINETIC TEMPERATURE AND COMPENSATION EFFECT FOR HIGH TEMPERATURE CRUDE OIL FOULING

The initial fouling rates of four crude oils were determined at a nominal bulk temperature of 315 °C, an initial heated wall shear stress of 13 Pa, and initial surface temperatures between 375 and 445 °C. These initial fouling rates ranged from 1.3(10-6) to 7.8(10-5) m2 K/kJ. Corresponding Arrhenius plots were linear with the initial fouling rates passing through an isokinetic temperature of 407.5 °C. A plot of the natural logarithm of the preexponential factors (7.6(104) – 5.2(1015) m2 K/kJ) versus the apparent activation energies (128 – 269 kJ/mol) was also linear, confirming the validity of the isokinetic temperature and the presence of the compensation effect. Below the isokinetic temperature, the relative fouling rates were Crude Oil C \u3e Crude Oil A \u3e Crude Oil D \u3e Crude Oil B; above the isokinetic temperature, the relative fouling rates were reversed (Crude Oil B \u3e Crude Oil D \u3e Crude Oil A \u3e Crude Oil C). Chemical characterization of a fouling deposit suggested that the dominant fouling mechanism at these conditions was coking with significant contributions from sedimentation (iron sulfide) and corrosion (~340 μm/yr) of the 304 stainless steel test material

OBSERVATION OF AN ISOKINETIC TEMPERATURE AND COMPENSATION EFFECT FOR HIGH TEMPERATURE CRUDE OIL FOULING

The initial fouling rates of four crude oils were determined at a nominal bulk temperature of 315 °C, an initial heated wall shear stress of 13 Pa, and initial surface temperatures between 375 and 445 °C. These initial fouling rates ranged from 1.3(10-6) to 7.8(10-5) m2 K/kJ. Corresponding Arrhenius plots were linear with the initial fouling rates passing through an isokinetic temperature of 407.5 °C. A plot of the natural logarithm of the preexponential factors (7.6(104) – 5.2(1015) m2 K/kJ) versus the apparent activation energies (128 – 269 kJ/mol) was also linear, confirming the validity of the isokinetic temperature and the presence of the compensation effect. Below the isokinetic temperature, the relative fouling rates were Crude Oil C \u3e Crude Oil A \u3e Crude Oil D \u3e Crude Oil B; above the isokinetic temperature, the relative fouling rates were reversed (Crude Oil B \u3e Crude Oil D \u3e Crude Oil A \u3e Crude Oil C). Chemical characterization of a fouling deposit suggested that the dominant fouling mechanism at these conditions was coking with significant contributions from sedimentation (iron sulfide) and corrosion (~340 μm/yr) of the 304 stainless steel test material