https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3458 n, the intermittency exponents µα based on individual and mixed sixth-order structure functions, the scaling exponents ζα(n) of the locally averaged energy and temperature dissipation rates approximated by (δα/δx)2, the flatness factors of the derivatives δα/δx, and the probability density functions (PDFs) of δα/δx, the increment δα and (δα/δx)2. It is found that v and θ are similar in terms of their intermittency characteristics. They are more intermittent than u. The scaling exponent ζv(n) is marginally larger than ζθ(n). The intermittency exponent µθ is smaller than µv based on the estimate of mixed sixth-order structure functions, while µθ is nearly equal to µv based on the estimate of individual sixth-order structure functions. The temperature dissipation rate is more intermittent than the turbulent energy dissipation rate, as indicated by τα(n). The flatness factor of δθ/δx is marginally larger than that of δv/δx. The PDFs of δθ/δx, deltaθ, and (δθ/δx)2 show the strongest departure from the Gaussian distribution.]]> Wed 11 Apr 2018 15:53:37 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:4357 Wed 11 Apr 2018 12:09:23 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:3136 Wed 11 Apr 2018 10:50:12 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:40307 Thu 07 Jul 2022 16:28:37 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:40289 0.9.]]> Thu 07 Jul 2022 14:57:36 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:9644 Sat 24 Mar 2018 08:35:26 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:13339 Sat 24 Mar 2018 08:17:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:17808 −4, where x₀ is a virtual origin, follows immediately from the variation of the mean velocity, the constancy of the local turbulent intensity and the ratio between the axial and transverse velocity variance. Second, the limit at small separations of the two-point budget equation yields an exact relation illustrating the equilibrium between the skewness of the longitudinal velocity derivative S and the destruction coefficient G of enstrophy. By comparing the latter relation with that for homogeneous isotropic decaying turbulence, it is shown that the approach towards the asymptotic state at infinite Reynolds number of S+2G/Rλ in the jet differs from that in purely decaying turbulence, although +2G/R_λ∝R⁻¹_λ in each case. This suggests that, at finite Reynolds numbers, the transport equation for ϵ¯ imposes a fundamental constraint on the balance between S and G that depends on the type of large-scale forcing and may thus differ from flow to flow. This questions the conjecture that S and G follow a universal evolution with R_λ; instead, S and G must be tested separately in each flow. The implication for the constant C_ϵ2 in the k−ϵ¯ model is also discussed.]]> Sat 24 Mar 2018 07:57:35 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:37033 θ, the mean dissipation rate of θ̅²/2, where θ̅² is the temperature variance. The analytical approach follows that of Thiesset et al. (J. Fluid Mech., vol. 748, 2014, R2) who developed an expression for ϵ_κ, the mean turbulent kinetic energy dissipation rate, using the transport equation for (δu)², the second-order velocity structure function. Experimental data show that complete self-preservation for all scales of motion is very well satisfied along the jet axis for streamwise distances larger than approximately 30 times the nozzle diameter. This validation of the analytical results is of particular interest as it provides justification and confidence in the analytical derivation of power laws representing the streamwise evolution of different physical quantities along the axis, such as: η, λ, λθ, R_U, R_Θ (all representing characteristic length scales), the mean temperature excess Θ₀, the mixed velocity–temperature moments uθ², vθ² and θ² and ∈_θ. Simple models are proposed for uθ² and vθ² in order to derive an analytical expression for A_∈θ, the prefactor of the power law describing the streamwise evolution of ∈θ. Further, expressions are also derived for the turbulent Péclet number and the thermal-to-mechanical time scale ratio. These expressions involve global parameters that are most likely to be influenced by the initial and/or boundary conditions and are therefore expected to be flow dependent.]]> Fri 07 Aug 2020 10:22:14 AEST ]]>