Auxiliary Bed Research Articles

Research on auxiliary bed - lifting device for the elderly

Although there are devices to assist the elderly to get out of bed in China, most of them are aimed at the disabled elderly or still need artificial assistance. For some old people with certain activity ability, there is no appropriate auxiliary equipment at present. Based on this background, the electric push rod and gear system are used to realize the back lifting, leg bending and auxiliary standing functions of the elderly when they get up and lie down. The matching design of connecting rod mechanism and gear mechanism is adopted to meet all the needs of the elderly when they get up and lie down with a simple mechanism.

New dynamic two-layer model for predicting depth-averaged velocity in open channel flows with rigid submerged canopies of different densities

The depth-averaged velocity is the commonly used engineering quantity in natural rivers, and it needs to be predicted in advance, especially in flood seasons. A model that can provide a unified physical foundation for open channel flows with different canopy densities remains lacking despite ongoing researches. Here, we use the concept of the auxiliary bed to describe the influence of momentum exchange on rigid canopy elements with varying density and submergence. The auxiliary bed divides the vegetated flow into a basal layer and a suspension layer to predict average velocity in each layer separately. In the basal layer, the velocity profile is assumed to be uniform. In the suspension layer, a parameter called “penetration depth” is applied to present the variations in velocity distribution. We also apply a data-driven method, called genetic programming (GP), to derive Chezy-like predictors for average velocity in the suspension layer. Compared to the hydraulic resistance equation for rough-wall flows, the new formulae calculated by the weighted combination method show sound physical meanings. In addition, comparison with other models shows that the new dynamic two-layer model achieves high accuracy in flow rate estimation, especially for vegetated flow with sparse canopies.

Mean Velocity and Shear Stress Distribution in Floating Treatment Wetlands: An Analytical Study

AbstractFloating treatment wetlands (FTWs) are efficient at wastewater treatment; however, data and physical models describing water flow through them remain limited. A two‐domain model is proposed dividing the flow region into an upper part characterizing the flow through suspended vegetation and an inner part describing the vegetation‐free zone. The suspended vegetation domain is represented as a porous medium characterized by constant permeability thereby allowing Biot's Law to be used to describe the mean velocity and stress profiles. The flow in the inner part is bounded by asymmetric stresses arising from interactions with the suspended vegetated (porous) base and solid channel bed. An asymmetric eddy viscosity model is employed to derive an integral expression for the shear stress and the mean velocity profiles in this inner layer. The solution features an asymmetric shear stress index that reflects two different roughness conditions over the vegetation‐induced auxiliary bed and the physical channel bed. A phenomenological model is then presented to explain this index. An expression for the penetration depth into the porous medium defined by 10% of the maximum shear stress is also derived. The predicted shear stress profile, local mean velocity profile, and bulk velocity agree with the limited experiments published in the literature.

New formulation for the effective relative roughness height of open channel flows with submerged vegetation

The friction factor f is a crucial parameter for scaling friction resistance and energy loss in open channel flows [11,16]. We propose an auxiliary bed for the distinctive flow structure arising from mutual effects of flow and vegetation. Using the auxiliary bed, a two-layer dynamic model with meaningful physical significance is established to modify equations for channelized flows with vegetation. This new approach divides the vegetated flow into two parts: a basal layer and a suspension layer. A parameter named ‘effective relative roughness height’, analogous to the relative roughness height of unvegetated open channels, is proposed to predict the friction factor of the suspension layer. By analyzing hundreds of datasets, a series of formulae are proposed based on the application of the effective relative roughness height. Comparisons show that the new formulae yield more precise estimates of the flow rate, Manning coefficient and Chezy coefficient than previously published formulae on the subject.