https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17032 a, ya, x and the transverse direction y (ε_{a, yhom}) and homogeneity in the transverse plane, (ε ), are assessed. All the approximations are in agreement with ε¯ when the distance downstream of the obstacle is larger than about 40 diameters. Closer to the obstacle, the agreement remains reasonable only for ε¯_a,x , ε¯_hom and ε¯_4x. The probability density functions (PDF) and joint PDFs of ε and its surrogates show that ε_4x correlates best with ε while ε_iso and ε_hom present the smallest correlation. The results indicate that ε4x is a very good surrogate for ε and can be used for correctly determining the behaviour of ε.]]> Wed 11 Apr 2018 12:08:09 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:15637 Sat 24 Mar 2018 08:23:45 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:26107 -4 (x is the streamwise direction). It is important to stress that this derivation does not use the constancy of the non-dimensional dissipation rate parameter C_∊ = ⋷u^'3/L_u (L_u and u' are the integral length scale and root mean square of the longitudinal velocity fluctuation respectively). We show, in fact, that the constancy of C_∊ is simply a consequence of complete SP (i.e. SP at all scales of motion). The significance of the analysis relates to the fact that the SP requirements for the mean velocity and mean turbulent kinetic energy (i.e. U ~ x^-1 and k ~ x^-2 respectively) are derived without invoking the transport equations for and . Experimental hot-wire data along the axis of a turbulent round jet show that, after a transient downstream distance which increases with Reynolds number, the turbulence statistics comply with complete SP. For example, the measured ⋷ agrees well with the SP prediction, i.e. ⋷ ~ x^-4, while the Taylor microscale Reynolds number Reλ remains constant. The analytical expression for the prefactor A_∊ for ⋷ ~ (x - X₀)^-4(where x₀ is a virtual origin), first developed by Thiesset et al. (J. Fluid Mech., vol. 748, 2014, R2) and rederived here solely from the SP analysis of the s.b.s. energy budget, is validated and provides a relatively simple and accurate method for estimating ⋷ along the axis of a turbulent round jet.]]> Sat 24 Mar 2018 07:39:53 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30203 q² diffusion term is negligible compared to advection term along the axis and the advection and energy dissipation terms dominate the budget. However, in the CC wake, aside from the advection and energy dissipation terms, the q² diffusion term also contributes significantly to the budget. At the region close to the centreline, the gain of the energy due to the contributions from the advection and diffusion terms is equal to the loss due to the isotropic dissipation, indicating that the isotropic dissipation rate ε iso is a good surrogate of the mean TKE dissipation rate ε.]]> Sat 24 Mar 2018 07:31:04 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34634 𝜖 =̅∈L/u'³(where 𝜖 is the mean turbulent kinetic energy dissipation rate, is an integral length scale and is the velocity root-mean-square) is investigated in decaying turbulence. Expressions for C_𝜖 in homogeneous isotropic turbulent (HIT), as approximated by grid turbulence, and in local HIT, as on the axis of the far field of a turbulent round jet, are developed from the Navier–Stokes equations within the framework of a scale-by-scale energy budget. The analysis shows that when turbulence decays/evolves in compliance with self-preservation (SP), C_𝜖 remains constant for a given flow condition, e.g. a given initial Reynolds number. Measurements in grid turbulence, which does not satisfy SP, and on the axis in the far field of a round jet, which does comply with SP, show that C_𝜖 decreases in the former case and remains constant in the latter, thus supporting the theoretical results. Further, while C_𝜖 can remain constant during the decay for a given initial Reynolds number, both the theory and measurements show that it decreases towards a constant, C_𝜖, as Re_𝜆 increases. This trend, in agreement with existing data, is not inconsistent with the possibility that C_𝜖 tends to a universal constant.]]> Fri 05 Apr 2019 15:31:13 AEDT ]]>