How to combine two or more WP_Query?

Hope this code may work for you.

$query1 = new WP_Query( array(
        'post_type' => 'product',
        's' => $searchStr
    ));

    $query2 = new WP_Query( array(
        'post_type' => 'product',
        'meta_query' => array(
            array(
               'key' => 'my_meta_key',
               'value' => $searchStr,
               'compare' => 'LIKE'
            )
         )
    ));

    $result = new WP_Query();
    $result->posts = array_unique( array_merge( $query1->posts, $query2->posts ), SORT_REGULAR );
    $result->post_count = count( $result->posts );