Simultaneous PIV and shadowgraph measurements of thermo-electrohydrodynamic convection in a differentially heated annulus.

To generate a radial force an alternating electric tension, HT <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="italic">V</mi><mo mathvariant="normal" fence="true" stretchy="false">(</mo><mi mathvariant="italic">t</mi><mo mathvariant="normal" fence="true" stretchy="false">)</mo></math> ht , is applied at the inner cylinder while the outer is grounded. The transition from the base unicellular flow to the thermoelectric instability occurs for all HT <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal"> </mi><mi mathvariant="italic">T</mi></math> ht between 6 kV and 8 kV. Figure 3 shows the post-treated shadowgraphs obtained for three different HT <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal"> </mi><mi mathvariant="italic">T</mi></math> ht and three different HT <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi mathvariant="italic">V</mi><mi mathvariant="italic">p</mi></msub></math> ht . The resulting shadowgraph exhibits an axisymmetric light intensity profile which is still visible for HT <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal"> </mi><mi mathvariant="italic">T</mi><mo>=</mo><mn>2</mn><mspace width="0.1667em" /><mtext>K</mtext></math> ht , and is not distinguishable for higher temperature differences between the two cylinders. [Extracted from the article]