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Showing posts from May, 2020

Ferro-cement OR Ferrocement

According to ACI (American concrete Institute), Ferrocement is a type of thin wall reinforced concrete commonly constructed of hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small size wire mesh. The mesh may be made of metallic or other suitable materials. Ferrocement differs from conventional concrete in that there is a higher ratio of steel to cement mortar. Ferrocement has many properties of steel and yet it will not rust. Although it looks and feels like concrete it can flex without cracking. By altering the steel/cement ratio we actually produce a material, which is superior to either steel or cement seperately. History of ferro-cement In 1940s, an Italian engineer Pier Luigi Nervi tested and presented in his paper, a new structural elements, an extremely thin plate of concrete made layers of small diameter wire mess and cement mortar with sand is used. In 1980, ACI gives standards of use and mixes  of ferro-cement. Prope

Orifice and hydraulic coefficients

The orifice is a small opening in the wall or base of a vessel through which the fluid flows. A mouthpiece is an attachment in the form of a small tube or pipe fixed to the orifice. Its length is usually two or three times the diameter of orifice. It is used to increase the amount of discharge. Hydraulic coefficients Coefficient of contraction :- It is defined as the ratio of area of jet at vena contracta (the points at which the streamlines first become parallel is called vena contracta) to the area of orifice. Coefficient of velocity :- It is defined as the ratio of the actual velocity of the jet at vena contracta to the theoretical velocity. Coefficient of discharge (C d ) :- It is defined as the ratio of the actual discharge through the orifice to the theoretical discharge. The coefficient of discharge is equal to the product of coefficient of contraction and coefficient of velocity. Coefficient of resistance :- It is defined as the ratio of loss of head in the orifice to

Centrifugal pumps

A centrifugal pump is a machine which converts the kinetic energy of the water into pressure energy before the water leaves its casing. The flow of water leaving the impeller is free vortex. The impeller of blades of centrifugal pump may have volute casing, vortex casing and volute casing with guide blades. The following important points may be noted for centrifugal pumps: a)  The manometric head is the actual head of water against which a centrifugal pump has to work. It may be obtained by using the following relations, i.e..   Manometric head is equal to Workdone per kg of water - Losses within the impeller Energy per kg at outlet of impeller - Energy per kg at inlet of impeller Suction lift + Loss of head in suction pipe due to friction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe  b) The discharge (Q) of a centrifugal pump is given by c) The manometric efficiency of a centrifugal pump is defined as

Notches and Weirs

A Notch may be defined as an opening provided in the side of a tank or vessel such that the liquid surface in the tank is below the top edge of the opening. It is generally made of a metallic plate. It is used for measuring the rate of flow of a liquid through a small channel or tank. A Weir   may be defined as any regular obstruction in an open channel over which the flow takes place. It is made of masonry or concrete. It is used for measuring the rate of flow in rivers or streams.  Comparison between Weirs and Notches   Important expressions used in Notches and Weirs (a) Discharge over a rectangular notch or weir (b) Discharge over a triangular notch or weir For a right angled V-notch (triangular notch) , ϴ = 90 ° (c) Discharge over a trapezoidal notch or weir ( also called Cippoletti weir) is equal to the sum of discharge over a rectangular notch or weir and the discharge over a triangular notch or weir (d) Discharge over a rectangular weir, according

30 Important questions of fluid mechanics

These are some important questions related to fluid mechanics that will help you in your studies. These questions will be helpful for both college exams and competitive exams. Questions Ques 1)  The centre of pressure acts ................. the centre of gravity of immersed surface a) at b)above c) below Ques 2) When a body floating in liquid, is given a small angular displacement, it starts oscillating about a point is known as   a) centre of pressure b) centre of gravity c) centre of buoyancy d) metacentre Ques 3)  A body floating in a liquid is said to be not in equilibrium if its metacentre lies below its centre of gravity a) agree b) disagree Ques 4) In one dimensional flow, the flow   a) is steady and uniform b) takes place in straight line c) takes place in curve d) takes place in one direction Ques 5) Coefficient of contraction is the ratio of  a) actual velocity of jet at vena contracta to the theoretical velocity b) loss of h