HWT showing a positively buoyant object.
HWT at NETL.
drop in the test section of the HWT at simulated ocean conditions of , depth.
Diagram of a particle suspended in the test section along with geometric parameters used to derive the equation of motion. Dimensions of the test section, used in the experimental setup, are as follows. Full height: . Radius at : . Diverging angle: .
Velocity profiles at the cross section of the test section obtained by automatic traversing Pitot tube for the range of flow rates .
Nondimensional drag force, , for a spherical particle as a function of Reynolds number and its linearization around the setpoint velocity .
Open-loop impulse response of the linearized equation of motion for a buoyant spherical particle in countercurrent fluid flow in a diverging pipe.
Axial flow velocity at as a function of the flow rate in the system.
Open- (solid line) and closed-loop (dashed line) responses (PID gains: , , ).
Response of system given by Eq. (24) with delay and noise to the step (top), impulse (middle), and square wave (period ) (bottom) perturbations for the two different control gain sets shown.
Square wave (period ) response of system given by Eq. (24) with delay and noise (PID controller gains: , , ).
Long-term drop behavior: (a) Open loop and (b) with PID control .
Short-term drop behavior: (a) Open loop and (b) with PID control .
drop response to square wave: (a) Open loop and (b) with PID control .
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