Potential Flow Velocity Research Articles

Induced barbiturate coma

Seven patients treated with deep sustained barbiturate narcosis to protect the brain and control intracranial hypertension underwent extensive monitoring. The epidural intracranial pressure (EDP) and arterial blood pressure (BP) were recorded continuously; serial records of the EEG, somatosensory evoked potential (SEP) and internal carotid artery (ICA) flow velocities by pulsed Doppler technique were obtained. Serum barbiturate levels leading to full suppression of the EEG did not change the central conduction time nor the configuration of the evoked responses. Monitoring the intracranial pressure (ICP), BP, and thereby, the cerebral perfusion pressure (CPP) gave valuable information on the patients' state and served as a guide for dosage and timing of barbiturate therapy, and facilitated supervision of adequate ventilation. Recording of EEG and SEP, monitoring of the CPP and ICA Doppler investigation offer prognostic information in these cases. When clinical deterioration occurs, these methods can predict and, in combination, give ample evidence for development of brain tamponade. Premature as well as unnecessarily deferred 4-vessel angiography, therefore, can be avoided.

Drag on an Oscillating Airfoil in a Fluctuating Free Stream

An analytical study is presented regarding the unsteady skin friction drag of an oscillating airfoil exposed to a fluctuating free stream speed. Both laminar and turbulent conditions are covered in the analysis. The unsteady potential flow pressure and velocity distributions required for the subsequent boundary layer analysis are obtained by an approximate development. The time-dependent boundary layer is solved by a finite difference scheme. It was found that depending on the values of the phase difference between free stream fluctuations and airfoil oscillations, reduced frequency, and amplitude of free stream fluctuations, the drag can either lead or lag the free stream.

A numerical experiment on two-dimensional turbulent separation

The simplest practical type of flow involving separation is that past a smooth flat plate with uniform velocity U0 at inlet followed by a linear adverse velocity gradient dU/dx = Constant (Fig. 1). At first the boundary layer is laminar up to the transition point xL. The turbulent boundary layer then grows with uniform potential flow velocity U0 outside the boundary layer up to the point x1 From x1 downwards the boundary layer grows in the presence of an adverse pressure gradient and finally separates at the point xs.

Mass transfer with chemical reaction from single gas bubbles

AbstractNumerical solutions of the equations that describe steady state, forced‐convection mass transfer around single circulating or noncirculating gas bubbles have been obtained for both first‐ and second‐order chemical reaction conditions. For the noncirculating bubbles, solutions have been obtained up to Reynolds numbers of 200 with Kawaguti velocity profiles used to describe the flow. In the case of circulating gas bubbles, Kawaguti profiles have been utilized up to Reynolds numbers of 80, while the potential flow velocity profiles have been used for higher Reynolds numbers. The numerical results for circulating gas bubbles have been compared with penetration theory for both first‐ and second‐order chemical reactions. For the case of noncirculating gas bubbles the solutions for physical mass transfer have been compared with the Ranz and Marshall correlation as well as with the results of Griffith and the more recent work of Tsubouchi and Masuda.