SIMULATION OF A COLD-STRESSED FINGER INCLUDING THE EFFECTS OF WIND, GLOVES, AND COLD-INDUCED VASODILATATION

The thermal response of fingers exposed to cold weather conditions has been simulated Energy balance equations were formulated, in a former study, for the tissue layers and the arterial, venous, and capillary b lood vessels. The equations were solved by a finite difference scheme using the Thomas algorithm and the method of alternating directions. A t this stage of development the model does not include any autonomic c ontrol functions. Model simulations assumed an electrical heating elem ent to be embedded in the glove layers applied on the finger. A 1.3 W power input was calculated for maintaining finger temperatures at thei r pre-cold exposure level in a 0 degrees C environment. Alternate assu mptions of nutritional (low) and basal thigh) blood flows in the finge r demonstrated the dominance of this factor in maintaining finger temp eratures at comfortable levels. Simulated exposures to still and windy air at 4.17 m/s (15 km/h), indicated the profound chilling effects of wind on fingers in cold environments. Finally, the effects of variabl e blood flow in the finger, known as ''cold-induced vasodilatation,'' were also investigated. Blood flow variations were assumed to be repre sented by periodic, symmetric triangular waves allowing for gradual op ening-closing cycles of blood supply to the tip of the finger. Results of this part of the simulation were compared with measured records of bare finger temperatures. Good conformity was obtained for a plausibl e pattern of change in bloodflow, which was assumed to be provided in its entirety to the tip of the finger alone.