All About Mechanical Engineering

Thermal equilibrium When there are Variation in temperature from point to point of an isolated system the temperature at very point has changed with time. This rate of change degrees and eventually stop. When no further changes are observed the system in said to be in thermal equilibrium. Laws of thermodynamics:- Zeroth law of thermodynamics:- This law states that when two bodies are in thermal equilibrium with a third body they are also in thermal equilibrium with each other. First law of thermodynamics:- These laws state that the heat and mechanical work are mutually convertible. To this law definite amount of mechanical work is needed to produce a definite amount of heat and vice versa.                         this law also state that the energy can neither be created not destroyed, through it can be transformed from one form to another. According to this law the energy ...

  Mach number and its importance :- The ratio of the velocity of the fluid in an on distributed steam to the velocity of the sound wave is known as Mach number. it gives us important information about the type of flow. In general, the flow of a fluid is diverted into the following four types depending upon the Mach number. 1) when the Mach number is less than Unity, the flow is called a subsonic flow. 2) when the Mach number is equal to Unity the flow is called a Sonic flow. 3) when the Mach number is between 1 and 6 the flow is called a Supersonic flow. 4) when the Mach number is more than 6 the flow is called hypersonic flow. Stagnation point:- In the flow where the velocity of the fluid is zero, called a stagnation point.

  Newton's law of viscosity :- According to Newton's law of viscosity does hair trace on a layer of a fluid is directly proportional to the rate of shear strain. The following important points may be noted for viscous flow a) fluid which has no viscosity is known as ideal fluid b) a fluid has a viscosity is known as aerial fluid. c) a fluid whose viscosity does not change with the rate of deformation or Shear Strain is known as newtonian fluid. d) a fluid whose viscosity change with the rate of defamation or Shear Strain is known as non newtonian fluid e) a flow in which the viscosity of fluid is dominating over inertia forces is called laminar flow. It take place at very low velocities.. f) iflow in which the inertia force is dominating over the is called turbulent flow. It take place at high velocities. g) wct at which the flow changes from the laminar flow to the turbulent flow is called 8 critical velocity. It is of two types otherwise lower critical velocity and higher cri...

 Section of Channel:- A channel is said to be most economical if a) It gives maximum discharge for a given cross sectional area and made shapes. b) it has minimum weighted perimeter c) lt involves excavation for the designed amount of discharge. The following Points are worthnothing 1) the most economical section of a rectangular channel is one which has hydraulic radius equal to half the depth of flow. 2) the most economical section of a trapezoid channel is one hydraulic mean Depth equal to half the depth of flow. 3) the most economical a rectangular channel is which has group side an angle of 45° with the vertical. 4) discharge through a channel of rectangular section is maximum when it's twice the Depth. 5) the discharge through channel of trapezoidal section is maximum when the slope side is equal to width at the top. 6) the discharge through a channel a circular section is when the depth of water call 0.95 time the diameter of the circular channel. 7) the discharge through ac...

  Bernoulli's Equation In Irrotational Flow we have obtained Bernoulli’s equation       This equation was obtained by integrating the Euler’s equation (the equation of motion) with respect to a displacement ' ds'  along a streamline. Thus, the value of C in the above equation is constant only along a streamline and should essentially vary from streamline to streamline. The equation can be used to define relation between flow variables at point B on the streamline and at point A, along the same streamline. So, in order to apply this equation, one should have knowledge of velocity field beforehand. This is one of the limitations of application of Bernoulli's equation. Irrotationality of flow field Under some special condition, the constant C becomes invariant from streamline to streamline and the Bernoulli’s equation is applicable with same value of C to the entire flow field.  The typical condition is the irrotationality of flow field. Proof: Let u...

  Compressibility Compressibility of any substance is the measure of its change in volume under the action of external forces. The normal compressive stress on any fluid element at rest is known as hydrostatic pressure  p  and arises as a result of innumerable molecular collisions in the entire fluid. The degree of compressibility of a substance is characterized by the  bulk modulus of elasticity  E  defined as Where  Δ  and  Δ p are the changes in the volume and pressure respectively, and   is the initial volume. The negative sign (-sign) is included to make E positive, since increase in pressure would decrease the volume i.e for  Δp>0 , Δ <0)  in volume. For a given mass of a substance, the change in its volume and density satisfies the relation D m  = 0,     D (  ρ  ) = 0    using     we get       Values of  E  for liqui...

  Ideal Fluid Consider a hypothetical fluid having a zero viscosity (  μ  = 0). Such a fluid is called an  ideal fluid  and the resulting motion is called as  ideal  or  inviscid   flow .  In an ideal flow, there is no existence of shear force because of vanishing viscosity. All the  fluids in reality have viscosity   ( μ  > 0) and hence they are termed as real fluid and their motion is known as viscous flow. Under certain situations of very high velocity flow of viscous fluids, an accurate analysis of flow field away from a solid surface can be made from the ideal flow theory.    Non-Newtonian Fluids There are certain fluids where the linear relationship between the shear stress and the deformation rate (velocity gradient in parallel flow) as expressed by the    is not valid. For these fluids the viscosity varies with rate of deformation. D ue to the deviation from Newton's law of viscosity they are...

Mathematical functions:- Following the continuous assumption, the mathematical description of the state of a moving fluid can be characterized by functions of the coordinates x, y, z and of the time t. These functions of (x, y, z, t) are related to the quantities defined for the fluid at a given point (x, y, z) in space and at a given time t, which refers to fixed points in space and not to fixed particles of the fluid. For example, we can consider the mean local velocity v(x, y, z, t) of fluid particles or fluid points, called the fluid velocity, and two thermodynamic quantities that characterize the fluid state, the pressure p(x, y, z, t) and the mass density (x, y, z, t), the mass per unit volume of fluid. Following the discussion of §2, two remarks can be done at this stage:  i). The fluid is assumed to be a continuum. This implies that all space-time derivatives of all dependent variables exist in some reasonable sense. In other words, local properties such as density pressur...

 BASIC PRINCIPLES OF FLUID:-    The application of the principles of fluid dynamics to the flow of air in underground openings. Airflow is induced from the atmosphere, through the intake opening, underground airways, return opening, and back to the atmosphere again by differential pressure between intake and return openings of the mine. This pressure differential is usually very small, in the order of 2 to 3% in most cases, when compared to the absolute pressure of the system. Therefore, volume and density changes are neglected without serious loss of accuracy or validity. Airflow in mines is also generally treated as steady-state, turbulent, and incompressible. However, in situations where the pressure, temperatures, and humidity changes are large and air conditioning processes are involved, calculations must incorporate the compressibility effect of air. Definition of A Fluid:- A fluid may be defined broadly as a substance that deforms continuously when subjected to she...

  Kinematic chains:- • Kinematic chain: links joined together for motion • Mechanism: grounded kinematic chain • Machine: mechanism designed to do work Link classification:-  Ground : any link or links that are fixed, nonmoving with respect to the reference frame  Crank: pivoted to ground, makes complete revolutions  Rocker: pivoted to ground, has oscillatory motion  Coupler: link has complex motion, not attached to the ground. Elements: 0: Ground (Casing, Frame) 1: Rocker 2: Coupler 3: Crank The “Ground” Link:-  When studying mechanisms it is very helpful to establish a fixed reference frame by assigning one of the links as “ground”.  The motion of all other links are described with respect to the ground link.  For example, a fourbar mechanism often looks like a 3-bar mechanism, where the first “bar” is simply the ground link. Determining Degrees of Freedom Two unconnected links: 6 DOF (each link has 3 DOF) When connected by a full joint: 4 DOF (each full joint eliminate...

 Linkage design:  Linkages are the basic building blocks of all mechanisms  All common forms of mechanisms (cams, gears, belts, chains) are in fact variations on a common theme of linkages. • Linkages are made up of links and joints. • Links: rigid member having nodes • Node: attachment points 1. Binary link: 2 nodes 2. Ternary link: 3 nodes 3. Quaternary link: 4 nodes Joint: a connection between two or more links (at their nodes) which allows motion; (Joints also called kinematic pairs). Joint Classification Joints can be classified in several ways: 1) By the type of contact between the elements, line, point, or surface. 2) By the number of degrees of freedom allowed at the joint. 3) By the type of physical closure of the joint: either force or form closed. 4) By the number of links joined (order of the joint). A joint with more than one freedom may also be a higher pair • Type of contact: line, point, surface • Number of DOF: full joint=1DOF, half joint=2DOF • Form closed (clo...