Thermal Convection by Marcello Lappa download in iPad, ePub, pdf
Newtonian viscosity is a law of friction for fluids. The viscosity of these fluids is roughly proportional to the length of time of flow or inversely proportional to the flow velocity. In the absence of an internal source, when the fluid is in contact with a hot surface, its molecules separate and scatter, causing the fluid to be less dense. Light the Sterno can and let the liquid heat up for a couple of minutes. The downward moving exterior is caused by colder air being displaced at the top of the thermal.
Granules on the photosphere of the Sun are the visible tops of convection cells in the photosphere, caused by convection of plasma in the photosphere. In this experiment, the shearing stress is larger you have to push harder on the silly putty in a horizontal direction to get the silly putty to flow and the rate of shear is much slower. Flow will occur faster if the silly putty is located in a relatively warm place.
Forced convection may happen by natural means, such as when the heat of a fire causes expansion of air and bulk air flow by this means. These are caused by the convection in the upper photosphere of the Sun.
This brings the sea breeze, air cooled by the water, ashore in the day, and carries the land breeze, air cooled by contact with the ground, out to sea during the night. The Sun warms the ground, which in turn warms the air directly above it. The stack effect helps drive natural ventilation and infiltration. As the moist air rises, it cools, causing some of the water vapor in the rising packet of air to condense.