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  2. Darcy–Weisbach equation - Wikipedia

    en.wikipedia.org/wiki/Darcy–Weisbach_equation

    Most charts or tables indicate the type of friction factor, or at least provide the formula for the friction factor with laminar flow. If the formula for laminar flow is f = ⁠ 16 / Re ⁠, it is the Fanning factor f, and if the formula for laminar flow is f D = ⁠ 64 / Re ⁠, it is the Darcy–Weisbach factor f D.

  3. Dimensionless numbers in fluid mechanics - Wikipedia

    en.wikipedia.org/wiki/Dimensionless_numbers_in...

    Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.

  4. Tsiolkovsky rocket equation - Wikipedia

    en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

    A rocket's required mass ratio as a function of effective exhaust velocity ratio. The classical rocket equation, or ideal rocket equation is a mathematical equation that describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity and can thereby move due to the ...

  5. Logarithmic decrement - Wikipedia

    en.wikipedia.org/wiki/Logarithmic_decrement

    The logarithmic decrement can be obtained e.g. as ln(x 1 /x 3).Logarithmic decrement, , is used to find the damping ratio of an underdamped system in the time domain.. The method of logarithmic decrement becomes less and less precise as the damping ratio increases past about 0.5; it does not apply at all for a damping ratio greater than 1.0 because the system is overdamped.

  6. Delta ratio - Wikipedia

    en.wikipedia.org/wiki/Delta_Ratio

    Mathematically, if the change in the numerator is similar to the change in the denominator, the delta ratio will be close to 1. Since the anions are unable to diffuse out of the bloodstream, while bicarbonate and hydrogen ions diffuse with ease (as H 2 CO 3, carbonic acid), the usual result will be closer to a delta ratio of 1 to 2.

  7. Dirac delta function - Wikipedia

    en.wikipedia.org/wiki/Dirac_delta_function

    The delta function was introduced by physicist Paul Dirac, and has since been applied routinely in physics and engineering to model point masses and instantaneous impulses. It is called the delta function because it is a continuous analogue of the Kronecker delta function, which is usually defined on a discrete domain and takes values 0 and 1.

  8. Dynamic modulus - Wikipedia

    en.wikipedia.org/wiki/Dynamic_modulus

    The ratio of the loss modulus to storage modulus in a viscoelastic material is defined as the ⁡, (cf. loss tangent), which provides a measure of damping in the material. tan ⁡ δ {\displaystyle \tan \delta } can also be visualized as the tangent of the phase angle ( δ {\displaystyle \delta } ) between the storage and loss modulus.

  9. Crack growth equation - Wikipedia

    en.wikipedia.org/wiki/Crack_growth_equation

    It is observed at low load ratios that the growth rate is most sensitive to microstructure and in low strength materials it is most sensitive to load ratio. [13] Regime B: At mid-range of growth rates, variations in microstructure, mean stress (or load ratio), thickness, and environment have no significant effects on the crack propagation rates.