What does attached flow mean

Post Fri Feb 08, pm. Post Tue Feb 12, am. Post Tue Feb 12, pm. Post Wed Feb 13, pm. News Headlines Calendar Chat. Development blog Features Glossary. Skip to content Laminar vs attached airflow Here are our CFD links and discussions about aerodynamics, suspension, driver safety and tyres. Please stick to F1 on this forum. Laminar vs attached airflow Post Sat Feb 02, am Someone was preaching to me recently that attached airflow is basically laminar airflow ie they're both the same thing.

As far as I understand it - he was wrong. And that you can have attached but turbulent airflow, ie not laminar, but he spoke with such confidence that I was unsure of my own proposition. Could someone help me clarify? Flow does not stay laminar on a surface for very long due to the viscous effects with the surface where there is considered to be no slip of the air.

The flow becomes turbulent due to the shear. You are correct in the fact that the turbulent boundary layer actually delays the separation of the flow from the surface.

However, if the adverse pressure gradient is high enough, the flow inverses upon itself and becomes completely separated. No Lotus. Remember Me. Members List. Mark Forums Read. January 16, , January 17, , Posting Rules.

Similar Threads. April 6, Working directory via command line. March 6, The Definition of the Flow Angle. February 23, July 20, Convergence Definition of Segregated Solver. April 18, LinkBack URL. Head is related to the velocity that the liquid gains when going through the pump. All the forms of energy involved in a liquid flow system can be expressed in terms of feet of liquid.

The total of these heads determines the total system head or the work that a pump must perform in the system. The different types of head—friction, velocity and pressure—are defined in this section. Friction head is the head required to overcome the resistance to flow in the pipe and fittings. It depends on the size, condition and type of pipe; the number and type of pipe fittings; flow rate; and nature of the liquid.

Velocity head is the energy of a liquid as a result of its motion at some velocity V. It is the equivalent head in feet through which the water would have to fall to acquire the same velocity or, in other words, the head necessary to accelerate the water.

Velocity head can be calculated using the following formula:. The velocity head is usually insignificant and can be ignored in most high-head systems. However, it can be a large factor and must be considered in low-head systems. Pressure Head Pressure head must be considered when a pumping system either begins from or empties into a tank that is under some pressure other than atmospheric. The pressure in such a tank must first be converted to feet of liquid.

A vacuum in the suction tank or a positive pressure in the discharge tank must be added to the system head, whereas a positive pressure in the suction tank or vacuum in the discharge tank would be subtracted. The following is a formula for converting inches of mercury vacuum into feet of liquid:. The different types of head are combined to make up the total system head at any particular flow rate. The descriptions in this section are of these combined or dynamic heads, as they apply to the centrifugal pump.

Total Dynamic Suction Lift h s Total dynamic suction lift is the static suction lift minus the velocity head at the pump suction flange plus the total friction head in the suction line. The total dynamic suction lift, as determined on a pump test, is the reading of a gauge on the suction flange, converted to feet of liquid and corrected to the pump centerline, minus the velocity head at the point of gauge attachment.

Total Dynamic Discharge Head h d Total dynamic discharge head is the static discharge head plus the velocity head at the pump discharge flange plus the total friction head in the discharge line. The total dynamic discharge head, as determined on pump test, is the reading of a gauge at the discharge flange, converted to feet of liquid and corrected to the pump centerline, plus the velocity head at the point of gauge attachment.

Suction lift exists when the source of supply is below the centerline of the pump. Therefore, the static suction lift is the vertical distance in feet from the centerline of the pump to the free level of the liquid to be pumped. Suction head exists when the source of supply is above the centerline of the pump.

Therefore, the static suction head is the vertical distance in feet from the centerline of the pump to the free level of the liquid to be pumped.

Static discharge head is the vertical distance in feet between the pump centerline and the point of free discharge or the surface of the liquid in the discharge tank.

Total static head is the vertical distance in feet between the free level of the source of supply and the point of free discharge or the free surface of the discharge liquid. The work performed by a centrifugal pump is a function of the total head and the weight of the liquid pumped in a given time period. The pump capacity in gallons per minute and the liquid specific gravity are normally used in the formulas rather than the actual weight of the liquid.

Pump input or brake horsepower BHP is the actual horsepower delivered to the pump shaft. Pump output or water horsepower WHP is the liquid horsepower delivered by the pump. These two terms are defined by the following formulas:. Pump characteristics—such as flow, pressure, efficiency and brake horsepower—are shown graphically on a pump curve.

The first item to look at is the size of the pump. The size of the pump, 2x is shown in the upper section of the graph. The numbers 2x indicates:. Some companies may have the number shown as 3x The larger of the first two numbers is the inlet. Pump speed rpm is also shown in the upper section of the graph and indicates performance at a speed of 3, rpm.

All the information is representative of this operational speed. Capacity or flow is shown along the bottom of the curve. The flow levels are shown for the operating speed of 3, rpm but indicate the effect of head as the outlet is throttled. The left side of the performance curve shows the head feet generated at the different flow rates. Multiple flow versus head curves are present on the graph see Figure 3.

Each one represents a different trimmed impeller size.