The bubble-free Belousov-Zhabotinsky reaction has been used to study the effects of centrifugal forces on autowave propagation. The reaction parameters were chosen such that the system oscillates naturally creating target waves. In the present study, the system was forced to rotate with a constant velocity around a central axis. In studying the effects of such a forcing on the system, we focused on target dynamics. The system reacts to this forcing in different ways, the most spectacular being a dramatic increase in the period of the target, the effect growing stronger as we move away from the center of rotation. A numerical study was carried out using the two-variable Oregonator model, modified to include convective effects through the diffusion coefficient. The numerical results showed a good qualitative agreement with those of the experiments.
The development of the wake velocity and tur-% T bulence profiles behind a cylindrical blunt based body aligned with a subsonic uniform stream was experimentally investigated as a function of the momentum thickness of the F approaching boundary layer and the transfer of mass into the recirculating region. Measurements were made just outside of the recirculating region at distances of 1.5, 2 and 3 diameters downstream of the cylinder. Results indicate that, even at these short distances from the cylinder base, the velocity profiles are similar. They also show that the width of the wake increases ~ with the thickness of the boundary layer while the velocity at the centerline decreases. Near wake mass transfer was found to 3" alter centerline velocities while the width of the wake was not significantly altered. Wake centerline velocity development as a function of boundary layer thickness is presented for distances up to three diameters from the base.
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A counterbalance valve, when correctly applied to a hydraulic circuit, modulates the flow of oil when lowering a load, with a crane for example, to prevent an overrunning condition. Under some unique operating conditions, they produce a high frequency, monotone noise that can be characterized as a “squeal.” The objective of the present work is to describe a series of experiments to investigate the flow induced noise in counterbalance valves. The experimental program not only quantified the noise level, frequency, and operating envelope in which “squealing” occurs, but also led to the formation of several hypotheses in an attempt to identify the cause of this noise. These included cavitation, oscillation of valve components, and oscillation of flow within the valve. Analyses of experimental results showed that oscillation of flow is the most likely cause of the “squealing” noise.
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