共查询到20条相似文献,搜索用时 31 毫秒
1.
Roel Verstappen 《Journal of scientific computing》2011,49(1):94-110
Large eddy simulation (LES) seeks to predict the dynamics of spatially filtered turbulent flows. The very essence is that
the LES-solution contains only scales of size ≥Δ, where Δ denotes some user-chosen length scale. This property enables us
to perform a LES when it is not feasible to compute the full, turbulent solution of the Navier-Stokes equations. Therefore,
in case the large eddy simulation is based on an eddy viscosity model we determine the eddy viscosity such that any scales
of size <Δ are dynamically insignificant. In this paper, we address the following two questions: how much eddy diffusion is
needed to (a) balance the production of scales of size smaller than Δ; and (b) damp any disturbances having a scale of size
smaller than Δ initially. From this we deduce that the eddy viscosity ν
e
has to depend on the invariants
q = \frac12tr(S2)q = \frac{1}{2}\mathrm{tr}(S^{2}) and
r = -\frac13tr(S3)r= -\frac{1}{3}\mathrm{tr}(S^{3}) of the (filtered) strain rate tensor S. The simplest model is then given by
ne = \frac32(D/p)2 |r|/q\nu_{e} = \frac{3}{2}(\Delta/\pi)^{2} |r|/q. This model is successfully tested for a turbulent channel flow (Re
τ
=590). 相似文献
2.
Mohammad Ali Abam Mark de Berg Mohammad Farshi Joachim Gudmundsson Michiel Smid 《Algorithmica》2011,61(1):207-225
Let (S,d) be a finite metric space, where each element p∈S has a non-negative weight w (p). We study spanners for the set S with respect to the following weighted distance function:
$\mathbf{d}_{\omega}(p,q)=\left\{{ll}0&\mbox{ if $\mathbf{d}_{\omega}(p,q)=\left\{\begin{array}{ll}0&\mbox{ if 相似文献
3.
We study the string-property of being periodic and having periodicity smaller than a given bound. Let Σ be a fixed alphabet
and let p,n be integers such that
p £ \fracn2p\leq \frac{n}{2}
. A length-n string over Σ, α=(α
1,…,α
n
), has the property Period(p) if for every i,j∈{1,…,n}, α
i
=α
j
whenever i≡j (mod p). For an integer parameter
g £ \fracn2,g\leq \frac{n}{2},
the property Period(≤g) is the property of all strings that are in Period(p) for some p≤g. The property
Period( £ \fracn2)\mathit{Period}(\leq \frac{n}{2})
is also called Periodicity. 相似文献
4.
Hazem M. Bahig 《The Journal of supercomputing》2008,43(1):99-104
In this paper, we study the merging of two sorted arrays
and
on EREW PRAM with two restrictions: (1) The elements of two arrays are taken from the integer range [1,n], where n=Max(n
1,n
2). (2) The elements are taken from either uniform distribution or non-uniform distribution such that
, for 1≤i≤p (number of processors). We give a new optimal deterministic algorithm runs in
time using p processors on EREW PRAM. For
; the running time of the algorithm is O(log (g)
n) which is faster than the previous results, where log (g)
n=log log (g−1)
n for g>1 and log (1)
n=log n. We also extend the domain of input data to [1,n
k
], where k is a constant.
5.
Given a “black box” function to evaluate an unknown rational polynomial
f ? \mathbbQ[x]f \in {\mathbb{Q}}[x] at points modulo a prime p, we exhibit algorithms to compute the representation of the polynomial in the sparsest shifted power basis. That is, we determine
the sparsity $t \in {\mathbb{Z}}_{>0}$t \in {\mathbb{Z}}_{>0}, the shift
a ? \mathbbQ\alpha \in {\mathbb{Q}}, the exponents 0 £ e1 < e2 < ? < et{0 \leq e_{1} < e_{2} < \cdots < e_{t}}, and the coefficients
c1, ?, ct ? \mathbbQ \{0}c_{1}, \ldots , c_{t} \in {\mathbb{Q}} \setminus \{0\} such that
|
设为首页 | 免责声明 | 关于勤云 | 加入收藏 |
Copyright©北京勤云科技发展有限公司 京ICP备09084417号 |