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2 Applied Mechanics and Engineering

2 1999

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The rheodynamics factor in the thermoregulation model

Shulman Z. P., Makhaniok A.

Applied Mechanics and Engineering

1999

Vol. 4, no spec.

169-176

The external or superficial heat or cold action has a strong influence on blood rheology and systemic and microvessels blood circulation. The tissue blood flow rate intensity is generally accepted to describe by Stolwijk's phenomenological model in the skin and Sekins's model in the muscle. We proposed an own model - a modification of Stolwijk's model, including influence of blood viscosity and vessel wall elasticity on the blood flow rate. A single equivalent vessel presents the arterioles and small arteries. The wall stress and the wall deformation of this vessel have described by Hook and Voigt-Kelvin models. The analytical expression has been obtained, which generalised Stolwijk and Sekins models. The quantitative analysis of the vessel wall elasticity influence on blood flow rate in the equivalent vessel has been performed out with the help of two dimensionless parameters, namely, the so-called "primary reaction" of the vessel at heating or cooling Dr and dimensionless complex p. The parameter 'DELTA''ro' is controlled by temperature. The p-complex is directly proportional to the transmural pressure value (Pinside-Poutside) and inverse proportional to elasticity modulus of the equivalent vessel wall. It has been found that the twofold increase of elasticity modulus decreases the blood flow rate on 30% at 'DELTA''ro' = 0,1 and < 1% at 'DELTA''ro' = 0,6. This means, that the elasticity modulus influence is increased with the stress relaxation of the vessel muscles. The new rheodynamics model of the thermoregulation was applied to the numerical simulation of the human body cooling process. The combined influence of vessel wall elasticity and temperature on blood flow rate and heat transfer for water hypothermia conditions has been considered. The tem-perature dependence of the apparent blood viscosity has been described by Arrenius' model. The results show the strong influence of blood viscosity and vessel wall elasticity alternations on blood flow rate and the heat transfer of man at moderate hypothermia (Tcore > 29-31oC). In the case water hypothermia at +10oC it has been shown that twofold increase of initial blood viscosity and wall elasticity modulus reduce the brain temperature on 3oC.

Flow of a Shvedov-Bingham fluid between surfaces of revolution with one porous wall

Walicki E., Walicka A., Makhaniok A.

Applied Mechanics and Engineering

1999

Vol. 4, no spec.

127-134

The influence of the wall porosity on the pressure distribution of a Shvedov-Bingham fluid flowing in the clearance between two surfaces of revolution is considered. As a result one obtains the formulae expressing the pressure distribution. An example of a squeeze flow between parallel disks is discussed in detail.