Bulk action of thermal stresses in a gas for continuum and transition flow regimes is studied. A set of new effects were revealed: gas flows due to thermal stresses in the absence of other causes of convection, force interaction of heated/cooled aerosol particles in a gas at rest, negative drag of strongly heated slowly moving particle. The effect of thermal stresses was confirmed experimentally. Gas states in the vicinity of thin permeable membranes and flows through them were studied theoretically and numerically. New types of Knudsen boundary layers adjusted to membrane surfaces were revealed. A temperature jump across Knudsen layer of new type resulting from the heat flux inside membrane was determined.
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