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The flow through the collector of a solar chimney power plant model on the roof of the Aerospace and Mechanical Engineering building at the University of Arizona was investigated numerically for the conditions of the experiment. The measured wall temperature and inflow velocity for a representative day were chosen for the simulation. The simulation was performed with a newly developed higher-order-accurate compact finite difference code. The code employs fifth-order-accurate biased compact finite differences for the convective terms and fourth-order-accurate central compact finite differences for the viscous terms. A fourth-order-accurate Runge-Kutta method was employed for time integration. Unsteady random disturbances are introduced at the inflow boundary and the downstream evolution of the resulting waves was investigated based on the Fourier transforms of the unsteady flow data. Steady azimuthal waves with a wavenumber of roughly four based on the channel half-height are the most amplified as a result of Rayleigh-Benard-Poiseuille instability. Different from plane Rayleigh-Benard-Poiseuille flow, these waves appear to merge in the streamwise direction. Oblique waves are also amplified. The growth rates are however lower than for the steady modes. Because of the strong streamwise flow acceleration, the growth rates decrease in the downstream direction. 

This paper reports on an experimental investigation of the flow through the collector of a solar chimney power plant which has been constructed on the roof of the Aerospace and Mechanical Engineering building at the University of Arizona. This model contains a central chimney which is a long tubular structure located in the center and a circular collector that employs the greenhouse effect to heat up the air under it. The chimney is 5.9m high and the collector radius measured from the center of the chimney is 4.13m. Measurements were carried out from April to June 2019. Several types of J thermocouples were mounted inside the collector at various radial locations to measure the air temperature both near the ground and the ceiling of the collector. A hot-wire probe (anemometer) was employed to measure the airflow velocity under the collector near the chimney inlet. A traverse system was designed and constructed, which allows the anemometer to be moved in the radial and circumferential direction under the collector. The height of the probe position above the collector ground can be adjusted by rotating the probe support along its longitudinal axis. A digital analog conversion system was used to convert the thermocouple and hot-wire readouts into binary data for processing via a LabVIEW interface. In parallel to the experiments, high-fidelity numerical simulations are being carried out for the conditions of the experiments. The simulations show longitudinal flow structures near the collector outflow that likely result from a buoyancy-driven instability.