Velocity distribution of wall-attached jets in slotted-inlet ventilated rooms

The wall-attached jets for ventilation in spaces have been drawn considerable interest for their benefit of high ventilation efficiency and thermal sensation. In this study, the velocity distribution of a wall-attached jet under isothermal conditions in slotted-inlet ventilated spaces is investigated by experimental and numerical approaches. The wall-attached jet issues air from a slot inlet that flows down along the surface of a vertical wall, impinging on the floor attached to the vertical wall and spreading over the floor surface. The results show that the flow field of a wall-attached jet can be divided into three regions: vertical attachment region (region I), horizontal air reservoir region (region II), and jet impingement region. The correlation equations for the centerline velocity decay and velocity profiles are obtained. For the fully developed jet in region I and II, the dimensionless velocity profiles can be expressed as u(0)/u(m)(y*)similar to(y*/b)(gamma) and u(0)/u(m)(x)similar to(x/b + K-h)(gamma), respectively, where gamma is a constant related to the momentum decay rate. Over the whole range of jet flow conditions in this study, the value of gamma is 1.11. Moreover, a unified exponential expression for the cross-sectional velocity profiles is proposed for both regions I and II. For the jet impingement region, the flow is complex and involves separation, reattachment, vortical flow, and pressure gradients. Large-scale vortices exist in the corner, and the vortices diminish as the jet inlet velocity increases. The current study can provide a theoretical basis for further engineering design applications of wall-attached jets for attachment ventilation.

Automated summary

Wall-attached jets for ventilation in spaces are efficient and provide good thermal sensation. The velocity distribution can be divided into three regions, and the momentum decay rate constant is 1.11. The study provides a theoretical basis for engineering design applications of wall-attached jets.