Table 1. Data collection from published literature.

We calculated the Reynolds numbers based on swimming speed (${\displaystyle {\mathrm{R}\mathrm{e}}_{\mathrm{U}}=\rho \mathrm{U}\mathrm{L}/\mu }$) and flapping velocity (${\displaystyle {\mathrm{R}\mathrm{e}}_A=2\pi \rho AfL/\mu }$), where $f=1/T$ is the flapping frequency. Missing values are either not applicable or not available.

Reference	Study type	System	Distance	Phase	ReU	ReA
Kim et al., 2010	Numerical	Flapping flags	Head-to-head	$\varphi \in [0,2\pi ]$	200 –400	–
Zhu et al., 2014	Numerical	Heaving flexible foils	–	$\varphi \in [0,\pi ]$	500	200
Ramananarivo et al., 2016	Experimental	Heaving foils	Tail-to-head	$\varphi =0$	103 –104	102 –103
Peng et al., 2018	Numerical	Heaving flexible foils	Tail-to-head	$\varphi =0$	509	200
Newbolt et al., 2019	Experimental	Heaving foils	Tail-to-head	$\varphi \in [0,2\pi ]$	103 –104	102 –103
Li et al., 2020	Experimental	Goldfish	Head-to-head	$\varphi \in [0,2\pi ]$	105	104
Kurt et al., 2021	Experimental	Pitching foils	Tail-to-head	$\varphi \in [0,2\pi ]$	9950	18,850
Heydari and Kanso, 2021	Numerical	Heaving plates	Tail-to-head	$\varphi =0$	–	–
		Pitching plates	Head-to-head	$\varphi =0$	–	–
Arranz et al., 2022	Numerical	Heaving flexible foils (3D)	Tail-to-head	$\varphi \in [0,2\pi ]$	176	200
Thandiackal and Lauder, 2023	Experimental	Fish-foil interactions	Tail-to-head	$\varphi \in [0,2\pi ]$	20·103 (foil)	50·103 (foil)
					40·103 (fish)
Becker et al., 2015 *	Experimental	Heaving foils	Tail-to-head	$\varphi =0$ ,$\pi$	–	102 –104
Park and Sung, 2018 *	Numerical	Heaving flexible foils	–	$\varphi \in [0,2\pi ]$	60 –1100	100 –1200
Dai et al., 2018 *	Numerical	Pitching + heaving foils	–	$\varphi =0$ ,$\pi$	440	600

^*Data not included in Figure 3.