User talk:Hassan Hamed Abd Alhachami

Flow induced vibration (FIV) might draw attention people who care in engineering disciplines. Even though the flow velocity runs out in a uniform direction, the D- Section, which was prepared in this experiment and subjected to various flow velocities and was sat up in various attack angles in front of fan tunnel, is non-symmetric. Many of the previous papers regarding the flow induced vibration. The tunnel of wind was used to experiment flow induced vibration of an elastic circular cylinder. The system which is consisted of one degree of freedom is circular, but the system is fixed with a ridge which is added on the surface of the body. The ridge is used to transfer small vibration amplitude that is called a galloping. The one degree of freedom systems are variety of cross section area, so all issues regarding a galloping should be discussed. One of studies has been finished regarding damping parameters of one degree of freedom. The damping parameters, which is represented as 𝐶∗=2𝑐𝑤𝑝 𝑈2, are very important in practical aspect for VIV response prediction of elastic structure. In this work, the cylinder is mounted by the spring as the canonical issue that could be used to create comparison between the suggested alternatives 𝑏∗ and 𝑐∗ with the performance of variables of mass damping. حسن حامد عبد الحجامي

The Derivation of Equation of Motion for D- Section
The one degree of freedom system, which is represented in the schematic diagram is consisted of the viscous damping coefficient Cs and the spring stiffness Ks. The equation of motion of the oscillator, which is driven translational galloping. My+ ̈Cy+̇ Ky=Fy The Sinusoidal force, drag and lift forces: Fy=−FD sinα−FL cosα (12) FD =12 𝓅 Vrel2 D CD (13) FL =12 𝓅 Vrel2 D CL (14) Where CL and CD are the lift and drag coefficient curves, 𝓅 the density of (flowing) medium and d effective area of the length cross section of the D- section. Now, the Sinusoidal force can be rewritten by substituting (13) and (14) in (12). Fy (α)=−(12 𝓅 Vrel2 D )(CD sinα+CL cosα)…. (15) Where y = 0. In this case, the motion might be small. When the motion is small, α can be considered equal to zero as figure 2 shows α value. Why α equalled to zero, it can be explained by as a result of the special Phenomena is called static divergence. This phenomenon's explanation is that no oscillation occurs but the model experiences a pure heave or pitch motion which is interpreted as a loss of vertical stiffness Therefore, the Taylor expansion can be defined below. Where the m is the mass per unit length, damping and stiffness coefficients c, and k per unit length. F(α)=−12 𝓅 Vrel2 D [CL0 +(CD +∂CL∂α)α ] (16) For small α, but α should be less than one, α can be written as below. In this case, the non-dimensional parameters should be written. α=sinα=𝑦̇Vrel (17) Substituting α in equation (15). F(α)=−12 𝓅 Vrel2 DCL0 −12 𝓅 Vrel D(CD +∂CL∂α)𝑦̇.. (18) After proofing all the parameters for each unknown symbol, now, they should be substituted in the main equation of motion: My+ ̈Cy+̇ Ky=Fy (19) =−12 𝓅 Vrel2 DCL0 − 12 𝓅 Vrel D (CD + ∂CL∂α)ẏ.….. My+ ̈[Cs+12 𝓅 Vrel D (CD + ∂CL∂α)]𝑦̇+K y−12 𝓅 Vrel2 DCL0 (20) Whereas the total damping and the damping ration. 𝐶𝑡𝑜𝑙𝑎𝑙=[Cy+12 𝓅 Vrel D (CD + ∂CL∂α)] (21) ζ=Cs2mw (22) Cs=2mζw (23) Substituting (23) in (20). The translational galloping equation of motion of D- Section can be defined as: Mÿ+[2ζsmωs+12 𝓅 Vrel D∂CL∂α+12 𝓅 Vrel DCD]ẏ+Ky−12 𝓅 Vrel DCL0 حسن حامد عبد الحجامي

Your submission at Articles for creation: Flow induced vibration (March 23)
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Robert McClenon (talk) 00:23, 23 March 2016 (UTC)