YES

(format LCTRS :logic QF_LIA)
(fun f1 1 :sort (Int Int))
(fun u_5 2 :sort (Int Int Int))

(rule (u_5 n_0 w_2_1) (+ n_0 w_2_1) :vars ((n_0 Int) (w_2_1 Int)))
(rule (f1 n_2) (u_5 n_2 (f1 (- n_2 1))) :guard (> n_2 0) :vars ((n_2 Int)))
(rule (f1 n_3) n_3 :guard (<= n_3 0) :vars ((n_3 Int)))

Confluent by Parallel Closedness with proof:
no critical pairs

Elapsed Time:  11.55 ms