Finite difference simulation of die swell for a newtonian fluid

The phenomenon of die swell for Newtonian fluids has been successfully simulated using a finite difference numerical method. The calculations predict the surface shape of Newtonian jets over a range of Reynolds numbers from 4.2 to 92.3 for both rectangular slits and cylindrical tubes. The calculated die swells for tubes compare favourably to experimental data. Velocity profiles and pressure distributions in jets exiting from slits or tubes are also predicted. The numerical data were incorporated into a momentum balance expression to demonstrate factors influencing this phenomenon. Other solutions were calculated to predict the effect of gravity and a sudden perturbation in flow on the resulting jet shape.     

Sperm in poor quality semen from bulls during heat stress have a lower affinity for binding hydrogen-3 heparin

Binding assays with [3H] heparin were performed using spermatozoa collected prior to, during, and following summer heat stress to dairy bulls. Ejaculates collected in August 1983 after a period of ambient temperatures exceeding 29.4 degrees C exhibited a high frequency of abnormal sperm, and motility was reduced in some samples. Sperm in samples collected during heat stress possessed dissociation constants for binding [3H] heparin ranging from 134.5 to 163.2 nmol. In contrast, sperm in semen collected prior to and after heat stress had significantly lower dissociation constants (higher affinity) for [3H] heparin, 12.9 to 56.4 nmol. The number of binding sites for [3H] heparin on sperm did not change among collection periods. It was concluded that the binding affinity for [3H] heparin may reflect membrane integrity of bull sperm.     

Quantification of alarm chatter based on run length distributions

In the process industry, alarms are configured on the control system to provide indication of abnormal events to the control room operators. In the presence of improper design of alarm generating algorithm or lack of appropriate tuning, alarms are announced more frequently than what is typically sufficient to alert the operator, a condition commonly known as ‘alarm chatter’. Chattering alarms are the most common form of nuisance alarms. The concept of run length is introduced in the alarm management context to study alarm chatter and an index is proposed to quantify the degree of alarm chatter based on run length distributions obtained exclusively from readily available historical alarm data. Chatter index hence plays a crucial role in routine assessment of industrial alarm systems. Prominent features of the proposed chatter index and its variant are demonstrated using industrial data.     

Laboratory investigation of inversion of heavy oil emulsions

Laboratory investigations have been undertaken to assess the suitability of heavy oil‐in water emulsions for pipeline transportation. The emulsions contained 65% oil in water and were prepared using polyethoxy nonylphenol surfactants. Two methods were employed for simulating the shear process which accompanies pipeline flow: a bench scale stirred vessel and a rotated pipe toroid. The progress of the emulsions towards inversion, at which point the oil becomes the continuous phase, was followed by measuring the surfactant concentration in the aqueous phase using liquid chromatography. At inversion the surfactant concentration falls below the threshold level required to sustain an oil‐in‐water emulsion. The experiments showed that the lifetime of the emulsion depends upon the initial surfactant dosage, the solids content of the oil, the intensity of shear and the nature of the shear process. Laminar flow was found to be less desirable than turbulent flow.