A series of hot smoke tests is underway in a warehouse for comparison with more realistic fire experiments. Hot smoke tests are used commonly in the fire safety assessment of large enclosures. COMPACT is used in the numerical prediction of the spread of smoke and hot gasses in the warehouse during hot smoke tests. The comparison of numerical results with the measurements indicate satisfactory agreement. COMPACT will be utilized next in the prediction of fire experiments, as a contribution to the use of CFD tools in the development of performance based fire codes.
Following from numerical predictions and large scale experimental verification, flow measurements are presented to show the effect of transverse wire vibrations on spectral measurements. It has been shown previously that if the first and second natural frequencies of a probe wire are close, it is expected to have favorable dynamic characteristics in turbulent flow. This expectation is confirmed with flow measurements. Further, the traditional sensing length to diameter ratio is reexamined for small scale measurements.
It has been observed that two types of defects in hot-wire probes affect application of the zero-wire-length dissipation technique. The first defect is related to the ratio of sensitive wire length to diameter, L/d, of the probes. Using hot-wire probes of L/d<160, lower dissipation rate values are measured at a given location in a flow than the corresponding zero-wire-length extrapolation line. This linear regression line of dissipation rate versus wire length is formed with the measurements obtained at that location using probes of L/d>160 that are also free of structural defects. The second defect is due to probe manufacturing errors. Faulty prong-wire connections have been observed to cause large amplitude wire vibration. The dissipation rate values measured with such probes are higher than the corresponding linear regression line.
A clutch has the duty of interrupting power transmission without shutting off the source. As expected from any friction dependent operation, a traditional clutch suffers from wear and dynamic instability. What is proposed in this paper is to employ a liquid with a controllable apparent viscosity to avoid the inherent problems of friction. Electro-Rheological (ER) fluids can reversibly change between the liquid phase and a solid-like gel phase in response to electric potential fields in the order of a few kV/mm. Therefore, it is possible to use ER fluids as power transmission agents. If the level of power transmission is the result of the phase change of an ER fluid, then such a design has no moving components, smooth operation, low power consumption and a fast reaction time. This paper details experiments to quantify the variation of the shear strength of an ER fluid as a function of its important parameters. Then, these values are used to predict the amount of power transmission. Although ER fluids have attracted significant attention in the literature, published works deal with investigations either in the molecular level or in pure application. To the best of the authors’ knowledge, this paper reports the necessary information to predict performance in a practical format for the first time.
The effectiveness of granular dissipation has been demonstrated earlier through experimental observations and simulations that use specified cylinder motion. Here, the development of a dynamic model is presented, where there is 2-way communication between the granular material and the container as a valuable design tool. The objective of this progress report is to summarize the predictions obtained for a rotating granular dissipater, using the Discrete Element Method (DEM) technique. Comparisons are made with earlier work in which rotation of the boundary is specified.
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