Reynolds number strong turbulence

Nq is strongly dependent on the flow regime, Reynolds Number, N e, and installation geometi y of the impeller. The flow from an impeller is only that produced by the impeller and does not include the entrained flow, which can be a major part of the total motion flow from the impeller. The entrained flow refers to fluid set in motion by the turbulence of the impeller output stream [27]. To compare different impellers, it is important to define the t -pe of flows being considered. 

Reynolds numbers from 10,000 to 25,000, at which strong evidence exists that under certain conditions, a viscoelastic fluid thread can interact with turbulence eddies and reduce the overall flow friction in the pipe... 

The results of our tentative calculations [formulas (41)—(43)] of the distance at which a stabilized regime is established and the braking and heat transfer cover the entire cross-section show the opposite whereas in the stabilized flow the dependence on the Reynolds number disappears, the distance at which this stabilization occurs is very strongly dependent on the Reynolds number. At our large Reynolds numbers, long before stabilization, at a distance of 5 105d/Re turbulization of the boundary layer takes place. 

An increase in Be indicates a competition between the irreversibilities caused by heat transfer and friction. At high Reynolds numbers, the distribution of Be is relatively more uniform than at lower Re. For a circular Couette device, the Reynolds number (Re = wr2lv) at the transition from laminar to turbulent flow is strongly dependent on the ratio of the gap to the radius of the outer cylinder, 1 — n. The critical Re reaches a value 50,000 at 1 n 0.05. We may control the distribution of the irreversibility by manipulating various operational conditions such as the gap of the Couette device, the Brinkman number, and the boundary conditions. 

The isothermal friction coefficients for the three inlet types showed that the range of the Reynolds number values at which transition flow exists is strongly inlet-geometry dependent. Furthermore, healing caused an increase in the laminar and turbulent friction coefficients and an increase in the lower and upper limits of the isothermal transition regime boundaries. The friction coefficient transition Reynolds number ranges for the isothermal and nonisotliermal (three different heating rates) and the three different inlets used in their study are summarized in Table 8-6. 

Standard k-s The most widely used model, it is robust, economical, and time tested. The Reynolds stresses are not calculated directly, but are modeled in a simplified way by adding a so-called turbulent viscosity to the molecular viscosity. Its main advantages are a rapid, stable calculation, and reasonable results for many flows, especially those with a high Reynolds number. It is not recommended for highly swirling flows, round jets, or flows with strong flow separation... 

In aU methods there is Hquid flow with unbounded and strongly confined flow. In the unbounded flow, any droplets are surrounded by a large amount of flowing liquid (the confining walls of the apparatus are far away from most droplets), while the forces can be either frictional (mostly viscous) or inertial. Viscous forces cause shear stresses to act on the interface between the droplets and the continuous phase (primarily in the direction of the interface). The shear stresses can be generated by either laminar flow (LV) or turbulent flow (TV) this depends on the Reynolds number R, ... 

---