In experimental turbulent flows, the estimation of the dissipation rate of turbulent kinetic energy, \(\varepsilon\), is a challenge. The dimensional analysis approach is the simplest of the many available strategies, where \(\varepsilon = C_{\varepsilon} k^{3/2}/L\). Although the proportionality constant, \(C_{\varepsilon}\), is commonly stated to be on the order of unity, there is little experimental evidence to verify this claim for zero-mean stirred-chamber configurations in general, nor is there detailed information on how \(C_{\varepsilon}\) might systematically vary with flow conditions. Given the importance of zero-mean chambers for both practical and fundamental studies on turbulent flows, reliable data on the magnitude of \(C_{\varepsilon}\) would be an asset. The goal of the present investigation is to rigorously determine \(\varepsilon\) in turbulent helium gas using medium-resolution particle image velocimetry (PIV) combined with the corrected spatial gradient method—these results lead directly to \(C_{\varepsilon}\). Helium maintains relatively large Kolmogorov length scales, \(\eta\), due to its high kinematic viscosity, making it possible to resolve spatial velocity gradients in strongly turbulent fields (\(k \le {17.6}\,\hbox {m}^{2}\,\hbox{s}^{-2}\)) with only modest magnification while avoiding many of the difficulties associated with micro-PIV. The results confirm that the vector spacing, \(\varDelta x\), must be less than \(\eta\) to properly calculate the spatial velocity gradients—a recommendation that has not been universally agreed upon. We provide comprehensive \(C_{\varepsilon}\) results up to \(Re_\lambda = 220\) by varying the fan speed, fan count, and chamber pressure. \(C_{\varepsilon}\) eventually falls to a value of \({\sim }0.5\), although the true asymptotic value of \(C_{\varepsilon}\)—if it exists—remains elusive.

在实验湍流中，湍流动能耗散率\(\varepsilon\)的估计是一个挑战。维度分析方法是许多可用策略中最简单的一种，其中\(\varepsilon = C_{\varepsilon} k^{3/2}/L\)。尽管比例常数\(C_{\varepsilon}\)通常被认为是在单位量级上，但总体上几乎没有实验证据来验证这种关于零均值搅拌室配置的说法，也没有详细说明关于\(C_{\varepsilon}\)如何随流动条件系统地变化的信息。鉴于零均值室对于湍流的实际和基础研究的重要性，关于湍流大小的可靠数据\(C_{\varepsilon}\)将是一项资产。本研究的目标是使用中分辨率粒子图像测速法 (PIV) 结合校正的空间梯度方法来严格确定湍流氦气中的\(\varepsilon\) ——这些结果直接导致\(C_{\varepsilon} \)。氦保持相对较大的 Kolmogorov 长度尺度\(\eta\)，因为它具有高运动粘度，因此可以解决强湍流场中的空间速度梯度（\(k \le {17.6}\,\hbox {m} ^{2}\,\hbox{s}^{-2}\)）只有适度的放大倍率，同时避免了与微型 PIV 相关的许多困难。结果证实向量间距\(\varDelta x\), 必须小于\(\eta\)才能正确计算空间速度梯度——这一建议尚未得到普遍认可。我们通过改变风扇速度、风扇数量和腔室压力，提供高达\(Re_\lambda = 220\)的全面\(C_{\varepsilon}\)结果。\(C_{\varepsilon}\)最终下降到\({\sim }0.5\)的值，尽管\(C_{\varepsilon}\)的真正渐近值（如果存在）仍然难以捉摸。