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Ordinary Differential Equation (ODE)

Application in Engineering Industry

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Invention of ODE

  • Ordinary differential equation was originally established by English physicist Isaac Newton and German mathematician Gottfried Leibniz.
  • The history of differential equations chronicles the evolution of "differential equations" from calculus.
  • Leibniz, the Bernoulli brothers, and others introduced differential equations in the 1680.
  • This was a little longer after Newton's "fluxional equations" in the 1670s.
  • Differential equations differ from standard mathematical equations.
  • In addition to variables and constants, they also include derivatives of one or more variables.

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Newton–Leibniz Years

  • Differential equations have a hazy genesis and history in terms of their precise chronology.
  • Secrecy, private publication concerns, and the intellectual "war"-like aspect of the conflict between mathematics and scientific discovery.
  • Isaac Newton wrote The Method of Fluxions and Infinite Series, which was not published until 1736, about 1671.
  • He divided differential equations of the first order into 3 classifications.
  • The first two classes contain solely ordinary derivatives of one or more dependent variables.
  • The third class of differential equations involves partial derivatives of a single dependent variable.

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Basic Concepts of ODE

  • In mathematics, an ordinary differential equation (ODE) consists of one or more functions of a single independent variable and their derivatives.
  • An equation that comprises a function with one or more derivatives is termed as a differential equation.
  • In the case of ODE, however, ordinary is used to describe the derivative of functions with a single independent variable.
  • It is feasible to have derivatives for functions with more than one variable in the case of other forms of differential equations.
  • Partial differential equation, linear and non-linear differential equation, homogeneous and non-homogeneous differential equation are the forms of differential equations.

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Definition

  • Ordinary Differential Equations are equations in mathematics that contain just one independent variable and one or more of its derivatives in relation to the variable.
  • In other words, the ODE is depicted as a relation with one independent variable, x, and a real dependent variable, y, along with a number of its derivatives.
  • y',y", ….yn ,…  in relation to x.

Order

  • The definition of the order of ordinary differential equations is the order of the highest derivative in the equation.
  • The general form of an nth-order ODE is as follows:
  • F(x, y,y',….,yn) = 0
  • Note that, y' can be either dy/dx or dy/dt and yn can be either dny/dxn or dny/dtn.
  • An ordinary differential equation of the nth order is linear if it can be represented as follows:
  • a0(x)yn + a1(x)
  • yn-1 +…..+ an(x)y = r(x)
  • The function aj(x), 0 ≤ j ≤ n is known as the linear equation's coefficients. If r(x) = 0, the equation is considered to be homogeneous. If r(x) is less than zero, the equation is said to be nonhomogeneous. Also, learn the differential equation of the first order here.

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Types of ODE

Autonomous Ordinary Differential Equations

A differential equation that is independent of the variable x is referred to as an autonomous differential equation.

Linear Ordinary Differential Equations

If differential equations may be expressed as linear combinations of y's derivatives, they are referred to as linear ordinary differential equations. These can be further categorized as follows:

Homogeneous linear differential equations

Equations nonhomogeneous linear differential.

Non-linear Ordinary Differential Equations

Non-linear ordinary differential equations are those that cannot be expressed as linear combinations of the derivatives of y.

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Examples of ODE

  • In these ordinary differential equations, the notations for derivatives are dy/dx = y', d2y/dx2 = y", d3y/dx3 = y"', and dny/dxn = yn. Here are some instances of ordinary differential equations.
  • (dy/dx) = sin x
  • (d2y/dx2) + k2y = 0
  • (d2y/dt2) + (d2x/dt2) = x
  • (d3y/dx3) + x(dy/dx) - 4xy = 0
  • (rdr/dθ) + cosθ = 5

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Applications of ODE in Mechanical Engineering

Newton’s Law of Coding

  • Newton's law of cooling states that if an object with temperature T(t) at time t is placed in a medium with temperature Tm(t), the rate of change of T at time t is proportional to T(t)Tm(t); therefore, T satisfies a differential equation of the form

T′=−k(T−Tm)

  • Here, k>0, as the object's temperature must decrease if T>Tm and increase if T<Tm.
  • We will refer to k as the medium's temperature decay constant.
  • In this section, we will assume that the medium is kept at a constant temperature Tm for the sake of simplicity.
  • This is another instance of constructing a straightforward mathematical model of a physical occurrence.
  • As with the majority of mathematical models, it has limits.
  • For instance, it is acceptable to believe that the temperature of a room remains roughly constant if the cooling object is a cup of coffee, but this may not be the case if the object is a massive cauldron of molten metal.

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Modelling with Second Order ODE’s: Undamped Free Oscillations

  • A mass-spring system without damping is a prominent topic of study in mechanical engineering and mathematics.
  • These are essentially theoretical because damping forces are ignored.
  • True systems have damping forces, as their free oscillations always cease in the end.
  • However, as I will explain, this specific system will continue oscillating forever, or until it is stopped by an external force.
  • As a linear spring with spring constant k, this spring conforms to Hooke's Law. The spring can withstand tension, extension and compression.
  • Also assume that the system is devoid of any air resistance or other damping effects. Consequently, energy is exchanged exclusively between the spring and the mass.

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Conclusion

  • One or more functions of a single independent variable and their derivatives make up an ordinary differential equation (ODE).
  • A differential equation is a function with one or more derivatives.
  • Normal describes the derivative of functions with a single independent variable in ODE.
  • ODE has been crucial in addressing engineering concepts.
  • Newton’s law of coding is such an example, which states that if an object with temperature T(t) at time t is placed in a medium with temperature Tm(t), the rate of change of T at time t is proportional to T(t)Tm(t).
  • The other example is modelling with second order ODE’s: Undamped free oscillations.
  • All students who intend to pursue an engineering course must be prepared to learn ODE concepts.